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Heres my friend gus g's site. great tires
Dave L.


welcome

• welcome
  
• tires
  
• gallery
  
• contact
  

SteveO
    Guys, the following question arrives in my inbox frequently so I am posting my reply here today for all to see.
"What is the ideal temperature to run on my Mac engine and what is the maximum I should run?"

Here's the reply....

   Generally speaking for sprint track running with a Mac engine 300-325 is a good number but you have to be careful to recognize that ambient conditions will change the number a lot. In very cold weather 300 degrees could be pushing it on the lean side of the mixture while in very hot weather you can get to 300 even with the mixture set very rich. 400 degrees on a Mac is very risky in any weather!
   The amount of smoke from the exhaust is a more reliable indicator than the temp you see on the gauge as is the spark plug color. In certain conditions you may see temp gauge readings approach 400 and yet there will still be a healthy fog of smoke even at the end of the longest straight. Trust the smoke over the gauge. On the other hand, if there is no smoke when the driver has been on the throttle for a good stretch that is a sign of possible trouble, regardless of the temp display readings.
   If you really want to learn the tuning process well you have to do “plug cuts” and correlate the temp readings to the plug color. A “plug cut” is basically a quick shut off of the motor at the end of a session. You need to drive the kart hard right up to the point where you have to let off to safely enter the pits and then stop the kart and the engine as soon as it is safe to do so. You don’t want to putt through the pits and let the plug cool off and get coated with fuel. No cool down laps… drive as fast as possible right to the time you are ready to leave the track. If the pit entrance is a long way from where you are pitted you shut it off and push the kart back to your spot.
   Once the engine cools down you remove the spark plug and examine the color and condition of the porcelain insulator as well as the side electrode. Medium to dark brown on the porcelain is ideal. If it is black and oily you are running too rich, if it is light brown or gray you are too lean. If the electrode is very dry and light in color you are too lean, it should be dark and slightly moist.
   Each time you run you look at the plug and note the color and the temp on the gauge and then record the info along with the ambient temp and also who is driving. Each time you check you can determine if any adjustment is needed to the carb. The pit man should also be watching the smoke level and note the amount at different parts of the track. That info should also be added to the notes. Remember that the smoke level should always be greatest when the driver first applies full throttle after lifting for a corner.
    The crew man should pick spots like 50 feet off the slowest corner and the last 50 feet of the longest straight to note the smoke each lap. Usually, as the engine gains heat over the first 3 to 5 laps the smoke density should progressively diminish but it should never disappear completely. When the engine is tuned well the smoke should be very faint on the second half of the longest straight when the engine is up to full temp.
   Driver weight and skill can have a big influence on the required jetting. Light drivers place less load on the engines so they can usually tune a little leaner. Fast drivers that keep the throttle mashed all the time need to run richer to keep the engine temps under control. Fast, heavy drivers really need to watch the mixture as that combination will build the most heat in the motor. A carb set for a driver that pushes the kart very hard will often be way too rich for a novice driver that lets off the throttle way before the corners and coasts a lot.
   Careful attention to the details while correlating the results with the sounds you heard while driving is the art of tuning. The experienced drivers that are good don’t need anything other than their ears to listen to the sound of the motor and their butts to tell them which sound is fastest without wrecking it.
Regards,
Steve

tom k.
    ill attest to 400 deg being too much lol
thanks for the info...always appreciate you sharing experience
tk

dave bright
    All on the money. And I can sure back up the part about heavy DRIVERS.

Gary Wlodarsky
    I very seldom run gauges but when I do, 340-350,,, makes me kringe......prolly should run em all the time...

New Castle. Jacksonville and Barnsville with the long straights...

Brian Thomas

    Squeaked one on the long straight at New Castle.

Walter Dale
    How did we ever survive in the old days when we used the color of the fins to know if we were too lean.

Lee Williams
    And for the real old folks, we'd spit on the head to see if it "fizzled" when the kart first came off the track. But I agree with Steve, having someone watch the smoke from the pits and signal the driver when the smoke stops is the best way to tell if an engine is lean. No smoke = melted piston most of the time.

James Waltz
    SteveO, a question.....
Your advice is always well considered and should always be listened to.
   I am curious about something.
I have run KT100's in racing situations for going on 20 years.The "magic" number on the KT is 450.

   At 450, the piston is starting to vaporize - and leaves a pretty sparkly coating on the plug.So, I tune to stay between 400 and 425.

   Obviously, this is a good bit higher than what you are recommending for our old style engines.
Would you know why? I am curious.
Is it perhaps because the cooling fins are much bigger on the KT's than on our old Mac's and Benders?

Alan E. Lidke
    James, don't let the size of the fins fool ya. I run an open 820 @ 460 degrees on my enduro. I'd sure never run a Mac at that.     


karl.ginter

    There are lots of variables that haven't been mentioned in this discussion, that impact greatly on a "safe" operating temperature for a McCulloch racing engine.
    Two variables that haven't been mentioned thus far are piston-to-cylinder wall clearance and piston composition. Back in the day, we'd run Macs with .0035 to .004 clearance, a real recipe for seizure.
Today, we know that .0065 to .0078 is much better and safer, in terms of both cooling and lubrication.
    Also, piston composition has a tremendous impact on high temperature "swelling". Wiseco pistons, for example, while pretty in appearance, have much lower silicon content than factory McCulloch or Burris pistons, and hence are prone to high temperature swelling, diminishing the piston-to-cylinder wall clearance, and making them more prone to high temp seizures.
    All things being equal, 300-350 degrees is an excellent heat range for both performance and safety in my experience(s). While SteveO's temp, fuel, and plug reading methodology sounds laborious, it's one of the few ways to accurately determine how an engine is performing, independent of a simple head temp reading - spot-on, as usual.

Eric A.

    I find this all very interesting! As a gasket maker I try to do my best to understand how all these things work together. My competitor in the gasket world makes gaskets from material that will withstand 1200 degrees and brags about that fact. In my tiny little brain I am thinking anything over 500 degrees will start to become one piece!

I know we are talking head temps here. Can someone tell me what the temperature of the exhaust manifold would be? Would that temp be consistent with head temps?

Ted Johnson
    Alan, ya gotta remember the 820 is a chrome bore engine, so the cylinder expands at very close to the same rate as does the piston. I run the 610 opens, and with the iron bore, you'd never DARE to run at anywhere near that temp. The 610 runs best at about the same as Steve says is good for a Mac. Of course, I run richer than optimum for performance, as I have no reason to squeeze out the max from my engines. Ted

 James Waltz
    Since we are on the subject of CHT, I thought I'd share an experience I had regarding sensors . I run MyChron instruments on my race karts. Starting with a MyChron-II and later with a MyChron-3 g0ld.
    The sensors are the same for both. They have a fairly long solid lead, then a spring flex protector, and then the actual thermocouple cable. These work great on my KT-100's.

   However, on my Benders they fail rather rapidly due I believe to the vibration of the Benders.@* These are $40 a pop at Comet, and breaking one per track day is not good - especially when it's two engines that are destroying them.
    I started looking for alternate products . I found some stuff on Ebay and Amazon that was like $7 each, and looked good, with a stainless steel 14 mm ring that goes under the plug . These were type K thermocouples, and you can re-wire the ends to whatever style connector you are using.
     I got a couple, wired them up and went out on the track. Funny, though, I was only getting a reading of like about 150 degrees. Definitely not correct.
    I tested these thermocouples against the original MyChron units. Immersed in an ice water bath they were spot on, and in a container of near boiling water they were also spot on.

   Now I was confused.
   I started looking more closely at the cheapo TC's. As it turns out, the location of the actual TC junction is quite important. The cheapo units have the junction maybe 10 to 12 mm away from the ring itself.
   I tested again, with just the ring itself actually immersed in the water. Did not get the same readings at all! It seems that the bit of metal between the rings and where the TC junction is located acts kind of like a fin, and exchanges heat with the air around it such that the ring and the TC joint are at quite different temperatures.
   Since MyChron does not have a low mass sensor, was to start looking for other kart sensors that were low mass.
Digatron sensors ended up being the right solution.
   You do have to re-wire the TC to the needed style of connector that MyChron uses, but this is just the sort of handiwork that we all are mostly pretty good at.

Ciao to all!

david luciani

    James,
seems like an excellent how to article for the forum.
how about a little how to tutorial on the rewiring maybe complete with pix.
and possibly the source for the cheapo ends.
dave l.


SteveO

    Guys,

Lot's of good point shared... glad I made the post.
   Right away, this thread shows how easily someone can get lost and have lots of problems if they rely on an "expert" to tell them what temp they should tune their engine to run!
    It's important to remember that a temp gauge is simply a reference point to allow the driver to "monitor" the engine once the correct jetting has been determined through the careful reading of the plug, observation of smoke, sound of the engine and performance on the track.
   With my vintage karts I don't even turn the gauge on the first session I run at any particular track. I tune by sound, feel and smoke while on the track. Verify my settings with a plug cut and if I am happy with all then I note the jet settings and the next time I take the kart out I will turn on the gauge to see what it is showing.
   Thereafter through the weekend I will keep an eye on the gauge to see if anything is changing and respond if I see something that concerns me.
   A good example of how different the readings can be would be as follows... In February I ran my Bug Sprint/101 kart at Adams and it ran great at 335 degrees. I took the same package to Newcastle in June and with generously rich carb settings compared to Adams the kart ran great and the gauge was showing 390-400 if I drove the kart hard for a full lap or more. Newcastle has several long hard pulls where the kart is at WOT much longer than the Adams layout and it was pretty warm back there in June. If I had tried to limit the CHT to the 335 I saw at Adams the engine would have been so rich I would expect a fouled plug.

   Let's talk about Jim's question... why the KT100 can be run so much hotter??? First lets talk about the two different types of heads used on the KT100s.
   The early heads have much more material around the combustion chamber so they dissipate heat much better and they generate a lower CHT when tuned for max performance. With the early old style heavy head the good number was 375 degrees.
   Leave everything the same and switch to the new style lighter head with the squish and volume the same and the CHT will read 75 degrees higher. Remember... no jetting change, no compression change... yet the gauge shows 75 degrees higher with the lighter head with less material.
   Point to consider.... never compare temp readings from one engine type to another because engine design and thermocouple placement can alter the number a lot.
    Back to the KT100 for a moment... why can the light new style head type Yamaha be run at such high temps like 450-475??? Simple answer.... they have no compression.
    The 11cc rule imposed by IKF and WKA is a completely arbitrary, artificially low compression ratio that arose out of an examination of the possible combination of parts in the first bunch of KT100s that arrived in the USA. The tech committee broke down a whole bunch of motors, assembled one with the combination of parts that would produce the highest compression ratio (smallest volume in the chamber) and measure the volume in the chamber.
    From that process they arrived at 11cc as the minimum volume any stock engine could show up with and made that the rule.
   The truth is, the 11cc rule is terrible for engine life and they should have set the volume at something like 9 or 9.5. Because the engines have extremely low compression ratios they are not at risk of detonation to the same degree that most other kart engines are so they can be run much leaner without going past the point where detonation occurs and kills the engines.
   The beauty of my original post is that the methods laid out work for all engine types on any kind of track and they are really useful when the damn gauge breaks!
Steve O'Hara

Kurt Rodgers
    "back in the day"
when the US820 was the class (late 1990's?), as they got them tuned and figured out, CHT temps in the 500º was not uncommon (but the fast setup).

" However, on my Benders they fail rather rapidly due I believe to the vibration of the Benders."


@*This was a fairly new failure to experience. It was determined by Digitron that the solder was melting at those temps. Digiatron developed a "hi temp" lead where they silver solder the pick up. That seemed to end that problem.

Paul F

    JW part of the problem with those cheap TCs is they are on a Stainless Steel ring. Stainless Steel conducts heat very poorly. The temp difference is then compounded by the distance from the heat. The rest of the TC is being cooled by the airflow from the fan more than the heat from the sparkplug and plug boss are providing it.
Actually it is not all bad. You can use them but you would have to get used to different readings.

James Waltz

    Paul.

The readings on the cheapo TC's was so far out I decided never to use them.

Kurt.

The failure is due to the long rigid lead moving around a lot, and fatiguing the rigid lead right where it is soldered to the ring and the associated pair of narrow extensions of the ring. I even tried making little brackets that attached to the cylinder shroud to support the rigid lead, but the shroud vibrates relative to the cylinder, so that did no good. It's a purely mechanical failure due to fatiguing of the hard metal-sheathed lead. They all failed in exactly the same place. I got real tired real quick of destroying two $40 TC's each race weekend. The Digatron TC's are the same price, but at least they survive indefinitely.

David.

The re-wiring is simple. All Type K TC's use red and yellow wires.

I just trim the Digatron TC leads to the length I want, and then use the standard MyChron connectors (I just happened to have a few spares, what with the failures), being sure to get the polarity correct. The parts are small so guys with really big hands might have trouble with the little screws and the little rubber ring that goes around the leads just inside the 2-piece yellow connectors.
Alan E. Lidke

    I was once instructed (many moons ago) that it is vital to maintain the thermocouple length as manufactured and to not alter it in order to assure accurate readings. Any truth to that? I never tested their theory to confirm.

Dick Teal
    All of the ISSPRO swept needle gauges require that the leads are not changed to be accurate. I used them on my 60's enduros with great results. They still make the gauges, Google them and read what they say.

Dick






Paul F
    Alan E. Lidke wrote:
"I was once instructed (many moons ago) that it is vital to maintain the thermocouple length as manufactured and to not alter it in order to assure accurate readings. Any truth to that? I never tested their theory to confirm."
Definitely not true within reason lengths. They work on the fact that when two dissimilar metal are in contact they create a voltage that is affected by temperature. The voltage is small so electro magnetic interference is an issue hence shielding. I could blab for ever so read this instead. https://en.wikipedia.org/wiki/Thermocouple

Dick Teal
    Paul,
The ISSPRO gauges use an EGT probe and that could be the difference. Long haul diesels use these every day.

Dick




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We are looking for an early/mid 70's Hartman single sprint kart roller, Clean, preferably in the Midwest area.
Thank you.

reboring an engine Sort of

comedy rebore of an engine
[url=https://www.youtube.com/watch?v=bT1nRq-cM7M&feature=youtu.be][/url]

bwa ha ha
dave l.

Heres the Gilson Excalibur. a veritable unicorn in the vintage racing kart world. They are extremely rare only about 20 known examples exist. They were made by The gilson Brothers lawn mower Co. . early frames were bolted together the later versions were rivited with aircraft rivits. Built in the Monoque style they were a stiff frame theory kart. While not really competative they were extremely cool.
enjoy
Gilson Kart Slideshow

here ya go
alakart slide show

ok so some guys may say i'm a little famous. but not for good reasons exactly.
i am famous for bonehead assembly moves at the track.
my best ones are usually with carburators,

usually it's something really simple like installing a carb backwards and covering the piulse hole. typically i'll get the motor running anyway and waste lots of time trying to tune in the carb.

lately i've been blowing leaves in between work and rain days. i have a nice echo pb770t that has been really good to me. but this year it's been running slightly under top revs and that annoys the crap outta me.plus it has begun stalling and seems to be getting hot a very bad thing for two strokes anytime. well since i'm such an "expert" on two stroke racing engines i figured i'll just fix the blower. first i checked the plug.it was well worn but good color. next i looked at the air cleaner seemed dirty but still usable. so i read up on other issues and one was debris getting inside the cooling fins. it's a big job to get in there but i figured maintenance called for an inspection.
so i took it down to the motor. first the fins were immaculate so no problem there. then i noticed the hose return for the primer pump was pulled out of it's grommet. . aha says i . it also explained the dirty oil soaked tank and the gassy smell i was hearing about from me sweetie. so i pushed it back in place washed everything re-assembled and ordered new filters and plug.

motor fired right up ran well so i figured problem solved.

NOPE was blowing leaves at rental and was getting annoyed by cold air blowing onto my hip.
motor was running bad again too. plus my tenant asked what's dripping from machine . turned out cold air was gas mix and i was soaked in it.annoyed my sweetie again with BIG gassy smell. called a buddy and went to his house to get a kart he'd picked for me. at same time he looked at machine. now a different hose had pulled free. i figured that was issue.

he didn't dis agree but while i was there he showed me a weird tool he "sometimes" had to use when he needed to adjust a modern two stroke carb. it was a tiny tube with a D shaped end. he told me as a tech he was allowed to use that tool and "sometimes" they were available on ebay. he also told me most adjusters on new carbs are tiny and hidden. i didn't pay much attention to that as it seemed not to have much to do with my machine.

kit arrived and i installed new filters and plug. fixed hose and ran machine. STILL ran poorly. then i went to the net thinking maybe someone else may have same issue.
turns out EVERYONE has this issue sooner or later. seems the carbs get a little gummed up and start running too lean. it's an EPA regulation that ONLY dealers are allowed to tune the carbs.but first they are required to replace all the filters and plug.
long story short it would be at least 200.00 to repair and the motor came ONLY be set to federal specs exactly. it doesn't matter if the motor runs well just the specs are met. to do that most carbs have to have the tiny plugs removed then a tiny tool is used to adjust. then the tamper proof plugs are re-installed. if they aren't the dealer can be fined $30,000.00 per incident. removing the tamper proof plugs by owner is a fine of $3250.00 and the tool is only available to trained dealer techs.

so now i knew why my buddy was "showing" me the tool. it was to prevent me from "accidentally" fixing my carb myself and risking a big fine. so naturally all i did was carefully take apart my carb and dis assemble and clean it. i did discover a tiny jet hidden in the top of the carb. right next to the throttle control. it had a D shaped head that my buddies tool would work on or maybe i could've made one myself from a tiny brass tube but luckily i knew NOT TO because some cranky fed might ketch me and fine my law breakin butt. i also knew not to adjust my fulcrum arm about .001 up to increase gas flow as that too would have been illegal. i re assembled the carb made sure not to disturb the high needle to be 1/2 turn more open and reinstalled the now clean carb. put everything back together and added a small hole so i could see the top of my carb where the leave it alone needle resides under when assembled. i'm silly that way. anyway tried it
and
NOW
IT STILL RAN CRAPPY.
actually way way worse.
it was acting like it wasn't pulling fuel i got it to run but not much.i kept thinking i've done this before but couldn't think of when. so back in shop everything apart big hissy fit and i ordered a new carb 16 bux china repop from ebay.
but i kept thinking what went wrong??,after some research i found that even if i wanted the rough tune spec if i had messed with the setting it wasn't legally available. all walbro could post was between 1.5 turns from closed to four turns but don't you the homeowner mess with it.
thinking whats to lose i decided to reassemble and try again. wasn't sure why i thought that. when i went to assemble i noticed i was installing carb with pulse hole away from engine.
THEN i realized why the way the engine was acting was familiar, i had assembled the DANG THING WITH THE PULSE HOLE AWAY FROM THE ENGINE.
after another hissy fit i assembled it with the pulse hole FACING the engine and tried again.
fired right up was a little low revving but i looked into the hole i'd drilled but i definitely did not fiddle with the fuel inlet control needle at all but then mysteriously it was running way better.
punch line motor now runs fine. i definitely didn't use the tool i didn't make to tune it to peak out that would be illegal.

rant
what i'd like to know is what moron is in charge of these rules??
the dang corn addled gas they sell dissolves aluminum which then messes up the hole diameters making the tool run crappy. it takes alot longer to get job done . that ='s more pollution not less. a regular tool user learns to keep their tools running best because they need them well tuned. so as usual the wackos create a law to save the enviorment and instead make thing worse.
end of rant

 
sorry for long story i'm bored tonight
dave l.
but it does run again and somehow the motor is peaking fine again.
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well did a few swaps this weekend.i managed to get a set of dico front 4" rims awesome as i just got a kart needing them.
found a guy selling transponders complete in box.he wasn't sure they held charge but i know how to replace the batteries. bought both for 55.00 but resold one right then to buddy for 30. i know they are big bux but he's a buddy so who cares. bought a bunch of front wheel bearings same guy and control arms a couple of modern wheel hubs front. paid small money. reason i got these deals was a guy selling out in four stroke was there. it pays to waste some time looking through ANY kart stuff bearing don't care what wheel they are installed in those were american made and cost a buc each.got an original margay tank 3.00 from another four stroke guy.found a rupp mini bike frame complete with tank,seat and clutch. got a really good price will be selling that soon.found another neat mini bike frame with front wheel with brake. wasn't gonna buy but at 20.00 couldn't leave it. got a decent yamaha motor found with 5 third bearing mounts a few odds and ends. another good buy.
i'll be putting those in store which will be reopened pretty soon just gearing up now. i saw the same early dead axle kart i've seen for several years now. the guy wants 300.00 firm for it. never budges on price. it's not worth 300.00 and even if he loses i can't see why he keeps dragging it around. just loading and unloading over the years is NUTS to me.

so found not much rare vintage but good stuff anyway.even made several new friends. one lives in ct his name is dave also. he has several simplexs. i have his number i hope will be touching base with him to get him to scotts event in july.
also met a guy that does c&c complete motor builds. he also has been thinking to join vintage hopefully he'll get into the sport. seemed like a knowledgable guy.

a friend went to a different swap meet than i. he got a rupp and what looked like a margay. he buys to resell the margay was sold before he left i got the rupp.
sadly he just missed by seconds getting a simplex. it had original rims clean frame with original paint AND a mint tear drop tank.
went for $ 60.00 so deal are still around. that's all i got
dave l

Original triple engine Fox
https://youtu.be/2CoK1K6njrw