max running problems

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m_kane

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Mar 7, 2016
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Long time story here. I bought max from guy who was trying to repair it and have had enought :ummm:.
Problem was that max won't run correctly. It did not rev as it should and backfired. Making things not easy, sometimes it did run quite good.

First I tried to use shotgun method to clean carbs. But one mixture screw was stuck and somebody did broke socket very badly. So I could not remove screw, I tried to drill it, use different removing tools, but it did not get out. So, I had to buy used carburetor. I used only body and move all parts from original carburetor. I cleaned all carbs and put then together. After that max ran great. I drove it one summer, maybe thousand kilometers or so. But after it sitted in garage few weeks, it was not running goog again :bang head:. Same symptoms, not revving and backfires. Pulling choke helps it get little more revs, but not good..
So I put it to winter sleep and yesterday I took it out from storage. Same symptoms are there of cource. I tried shotgun method and flush carbs a little (opened screws to empty fuel bowls and ignition on, that fuel pump pushed new gas in). No effect. It starts, and runs at idle, not good but runs. If I give him throttle, he freezes in 4-5000 revs and starts to cough and can backfire. Opening choke it revs more momentarily.
So, it seems that max does not get fuel enought? I tried to check air leaks from intake manifold. Tried with air filter housing on or off. Tried to adjust idle mixture screws, default they were 3 turns open.
Strangely, I have not o-rings in mixture screws. Only spring and plate. Are they necessary? At least they do not cause this problem, as it did ran good a long time without them.

What should I do next? Taking carbs apart does not sound good because I just cleaned them. Otherwise, symptom is just same than before cleaning them.
Could it be cdi problem? Maybe it is possible that broken cdi can work weeks ok and then fail again?

One way to go is buy carb rebuild kits and new manifold rubbers, as they are not in very good condition. But is there any kits available to fix carbs? I don't want to take them apart and rebuild with old parts. Last time I did that, there was no visible dirt or debris anywhere.

Sorry about bad english, I am from Finland :icon_rolleyes:
 
Last edited:
Found the problem.
One fuel hose was blocked and one spark plug was malfunctioning in higher rpm's.
 
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