OK, cant get one of my Mc91's tuned. Fussed with carb. After rev up idles way down almost stalls, then revs up to high idle. Acting like an air leak... Switched carbs because it's easy. No change. Pull engine, pressure check holds 18-20 lbs all day..... Check timing, dead on. Reinstall carb and header and put back on kart. Won't start!! Got spark, got compression, got fuel..... Scratching head.
(07-24-2018, 06:20 PM)Al Peckenpaugh Wrote: [ -> ]OK, cant get one of my Mc91's tuned. Fussed with carb. After rev up idles way down almost stalls, then revs up to high idle. Acting like an air leak... Switched carbs because it's easy. No change. Pull engine, pressure check holds 18-20 lbs all day..... Check timing, dead on. Reinstall carb and header and put back on kart. Won't start!! Got spark, got compression, got fuel..... Scratching head.
check to make sure you don't have a poor seal where the fuel line connects to the carb.
Steve O'Hara
throw tillotson in the weeds and put a BDC on it ...just joking
will it fire on prime ..??
if not maybe crankcase is full of fuel ..??
hears a good one..if you aint already ... try new spark plug ..??
only suggestions ..
I haven't gone out there yet but I left it all open hoping to dry it out over night. I took it off to pressure check it. There may have been a load of fuel in the crankcase and I had it tipped all directions checking pressure. Tried plug. Saw fuel going through carb. I'll pull another engine out of the box if I gotta...... Leaving for Avon Thurs AM
Fuel line clamped to carb w/ safety wire. It's getting fuel.... Still hoping for a flooded engine
Pulse Hole gasket leak? I had this happen in a hater digger last week.
sounds like a blocked pulse hole to me.
i have lots and lots of experience doing that.
some manifolds will reverse top and or reed block with ease like the single gem 6 reed.
any mis alignment blocking pulse will let motor run then starve.
i even was running the mc10 on cuddeback with reversed pulse ran 3/4 of track would start acting up , i'd hand choke it and it spin back up till the kart ran 3/4 track again samer issue.
finally tought to check alignment.
other thought is lifted or worn out reeds that'll do something like that too.
gonna miss seeing you guys this year personal family stuff came up.
gotta stay close to home.
d
maybe put new O rings on needles ..tillotson hl and hr have give me troubles exactly what you described specially on low side...mine the O rings got hard as rock 6 months or less ..
(07-25-2018, 11:16 PM)steve miller Wrote: [ -> ]maybe put new O rings on needles ..tillotson hl and hr have give me troubles exactly what you described specially on low side...mine the O rings got hard as rock 6 months or less ..
Similar problem on one of my Macs.
Good pressure check.
Won't idle, just runs wild with a few different carbs!
I put it back on the shelf, but I will listen here for ideas.
I like Dave's pulse hole misalignment idea and I will try swapping the manifold out.
t
I switched the engine with a fresh one off the shelf... I'll see how it works when we get to Avon later today. It's on my dual so if it doesn't work, I'll run something else. That dual whips my ass anyway....
I'll look into that other engine later. I'll post if I find anything conclusive.
I had a similar problem with an 820. One of the reed petals had broken off. It ran, but ran very funny, including funky idle.