Help needed with MC9

[Michael Drechnowicz]

I am trying to get my MC-9 running for Avon. At the end of last year it was not running well, and would take a bilt of tinkering to get it to start. run. So over the winter, I replaced the carb gaskets, adjusted the fulcrum. It holds pressure fine and pops off around 20 psi (my gauge has a large scale, 5psi per tic, so I am not sure of the exact pressure but around 20). It holds the pressure for a good amount of time.

When I start it, I have to play around with the throttle and choke it to get it to start. Once started it does not want to take the gas, it bogs down. If I keep playing with the throttle, opening closing, it eventually will run ok but as soon as I idle it back down, it again does not want to take the gas, play around and it eventually will run well again.

I started with idle screw at 11/4 and hi speed at 1 1/2. I tried turning the idle both in and out and could not get it to run better consistently.

This is the engine I was intending to run at Avon in the historic class. My only other one is a US motor 820 which by the VKA rules is not legal in historic.

If would appreciate any help in solving this issue. I am kind of new to this and am not sure where to go from here. I don't want to come to the event with an engine that is not running.

Thanks for your time,

Michael

[John Wolkiewicz]

I was recently having trouble and I put a new fuel line with tight zip ties and voila ran perfect

[ted johnson]

Michael, I just emailed SteveO because I haven't teased a flatback for over 50 years. Maybe he will be able to help. If he gets a chance to email me back, I will post his answer here. Ted

[thomas kelley]

if its a bdc then it sounds like a duck bill problem
tk

[ted johnson]

Michael, please check your PM's for Steve O'Hara's phone number. He sent me his number and said for you to call him. He's extremely carb savvy. Ted

[steve miller]

if I had to guess id say small flat back ..?? 
pretty sure you cant use BDC in historic class ..??
if its small flat back good chance it needs new seal on the needles and I think 20 way to high pop off ..ill check mine but I think 12-15 is what I use ..I think .. 
ill be there mid day thurs.. im no engine god or super tuner but my junk most always runs ..maybe I can help..

[Michael Drechnowicz]

if I had to guess id say small flat back ..?? 
pretty sure you cant use BDC in historic class ..??
if its small flat back good chance it needs new seal on the needles and I think 20 way to high pop off ..ill check mine but I think 12-15 is what I use ..I think .. 
ill be there mid day thurs.. im no engine god or super tuner but my junk most always runs ..maybe I can help..

It is a flat back, no duckbill. Ted put me in touch with Steve O'Hara who was able to help me get the engine running. Well at least it ran today! I would appreciate help in fine tuning it at the track. I am trying to make it there on Thursday. Always eager to learn a little more about these engines. I don't know if you remember me but I was pitted next to you last fall at Cuddy. I had the red McCulloch R-1 kart.

Michael

[Paul Hunter]

Hi Michael, will you share with us what the problem was.
See you at Avon
Paul

[Michael Drechnowicz]

Hi Michael, will you share with us what the problem was.
See you at Avon
Paul

Sure, I'll give what I will call "the readers digest version" of what Steve had me do after asking me what the engine sounded like, how much smoke was produced and any other information I could give. I had replaced the needle, pump and metering diaphram and adjusted the lever and checked the pop off pressure. What Steve asked was if I had flow checked the carb. I did not and so he gave me instructions on how to do it which follows. When the carb is disassembled, there are two round soft plugs, one small, one large. Next the small one is a small hole. What Steve had me do is to inject water into the hole with the throttle open and the low speed needle screwed out 2 or 3 turns. Looking into the carb throat from the bottom of the carb, there are 3 small holes. What was expected is that the water should flow from all 3 holes. I only had water from 2 of them, the one furthest from the bottom was clogged. I continued injected water and finally freed up the clog and had flow from all the holes. There is also another hole under where the lever is recessed in the carb and I also injected water thru there and it should come out of a hole in throat at the other end of the carb (looking from the top) and that was fine. Steve also had me "squish" the spring under the lever to lower the popoff pressure a little. I then reassembled the carb and set the needles to where he recommended. I started the engine and eventually after adjusting the needles and rechecking the level of the lever in the carb, got it to run. I ran it on my street a couple of times and it seemed to be good enough. I am hoping that someone (thanks for the offer steve miller!!) will be able to help me fine tune it.

I really appreciate the help that Steve provided and the time that he took to discuss my problem since I would never have known to check that there should be flow from the 4 holes and how to check it. This website and the people that respond to questions are an invaluable resource to s novice, such as me, in this hobby.

Michael

[Paul Hunter]

Interesting, never heard of the flow check before, thanks for sharing Michael.
Paul