Engine issues

rainman

rainman

Member
After completely rebuilding my open 131 reed Italsistem on methanol to the same specs it
was before when it was running perfect before it started messing up I am having same issue I had last time. Engine won´t go over 10,500 rpms once in the track. Only problem I found was the lower rod bearing wasn´t in good shape and allowed too much play, which also caused some light damage on rod end but I decided to replace rod anyway. We changed seals, case bearings, pin, check top end which had a piston/ring/pin with only pne race on it and everything seemed to work fine when we run it at lower rpms to allow bearings and other parts get oil and seat properly. Carb was also checked, pop off and needle set properly, and gaskets replaced. My Birky clutch only has a race since rebuilt too. I went to race at Brunswick Speedway last Saturday for the VUAS race and it started great, no issues, but once at the track started cutting at 10,500 rpms, well basically it won´t reve over these rpms. I found out carb was missing one of the screws that hod all the stacks together but carb was still tight so I put one and funny thing I saw the screen wasn´t there either while trying to look for debris, but seemed to me very clean. Tried again and same issues. Changed coil and and gas just in case and same issues again. Never had any issue with this carb which was checked and was fine anyway, but carb and ignition rotor are the only things i haven´t replaced. I would like to see if we can fix it before Saturday so I can make it to Amelia though I don´t have much time. What do you think?
 
Check the reeds closely.& grounds on engine. we have to rebuild carbs completly every couple shows. Ron
 
True. I´ll check carb again and reeds, but last time when I 1st had that issue reeds and carb were fine. Can the ignition work fine and then just ness on top? Not so common but can´t find any other reason. As I said I tried with another coild too. Thanks, Ron.
 
I've had a bag plug do that to me. Check the end of the spark plug wire too. The spark plug cap should unscrew from it. Snip the 3/8" of the wire off and screw it back on. Also check that the tip the of spark plug is screwed all the way on and is tight.
Mike
 
MikeGrady said:
I've had a bag plug do that to me. Check the end of the spark plug wire too. The spark plug cap should unscrew from it. Snip the 3/8" of the wire off and screw it back on. Also check that the tip the of spark plug is screwed all the way on and is tight.
Mike
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I checked that, Mike. As I said I changed complete coil and of course I tried different spark plugs. Thanks Mike.
 
Hi Rainman,
I don't what it is but maybe a few things to think about:
1. ground strap must be grounded to engine then the coil
2. pulse hole on carb must be clear all the way thru to crankcase, also the pulse hole passage must NOT be vented or leaking anywhere b4 it enters the case sometimes gasket get torn/split and engine starts runs fine when case pressures go up all is lost do to split gasket
3. throttle linkage OK?
4. fuel line flows freely?
5. bad plug cap or burned plug wire ends
6. bad spark plug
7. flywheel key OK?
that is about I can think of right now.
Mike Berg
 
Magmo said:
Hi Rainman,
I don't what it is but maybe a few things to think about:
1. ground strap must be grounded to engine then the coil
2. pulse hole on carb must be clear all the way thru to crankcase, also the pulse hole passage must NOT be vented or leaking anywhere b4 it enters the case sometimes gasket get torn/split and engine starts runs fine when case pressures go up all is lost do to split gasket
3. throttle linkage OK?
4. fuel line flows freely?
5. bad plug cap or burned plug wire ends
6. bad spark plug
7. flywheel key OK?
that is about I can think of right now.
Mike Berg
Click to expand...

Mike, it is a reed, no pulse to crankcase. Flywheel? Guess you mean the igition stator or rotor. Key is fine too. We checked all this when we rebuilt engine after 1st time this happened. Throttle perfect too, opens butterfly perfect, and returns perfectly too, tried different spark plugs, changed fuel line and check it flows good, tried with another coil (by the way, it is a Motoplat), it starts and runs, so I can guess wiring should be fine, and we pressure checked engine, no leaks, no leaks. It is driving me crazy. Thanks, Mike.
 
Rainman

Mike is talking about pulse hole where carb bolts to manifold and that holes all line up including reed block and are not covered. What does it do on the stand with no load? Does it rev above 10500 then. How good is your tank vented. Where is your clutch slip set. Also have you checked the pipe to see if it could be plugged.

Roy
 
I sure hope you don't pull the plug wire off to stop your engine, it's the best way to ruin your stator that I know of. that's why when any engine I race has a Motoplat, I always bring every one I own, you never know. I also had several KT's that I have owned over 20 yrs., they would start and run fine, then 1/2 way through a feature race they would shut right off, I now but all new ignition parts for my Yammi's and it seems to have fixed the problems.
 
Put it in a box and send it to a reputable builder with a dyno. They will find the problem in way less time than any of us shooting ideas when we can't put eyes and ears on it.
Mike
 
I have seen Motoplat stators go bad like that. As old as they are I would put a new PVL on it to eliminate any ignition problems as the wires inside get old a brittle. I know its a chunk of money to shell out for a new one, but piece of mind.jmo
 
pulse hole

rainman said:
Mike, it is a reed, no pulse to crankcase. Flywheel? Guess you mean the igition stator or rotor. Key is fine too. We checked all this when we rebuilt engine after 1st time this happened. Throttle perfect too, opens butterfly perfect, and returns perfectly too, tried different spark plugs, changed fuel line and check it flows good, tried with another coil (by the way, it is a Motoplat), it starts and runs, so I can guess wiring should be fine, and we pressure checked engine, no leaks, no leaks. It is driving me crazy. Thanks, Mike.
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Check the pulse hole that passes from the carb thru the intake manifold then thru reed cage, and ALL the gaskets each gasket must be unmolested meaning a round complete round hole for the pulse to pass thru NO slots NO tears, this happened to us last summer engine would not run past clutch engagement speed without serious pause ( lean condition ), replaced one gasket engine ran perfect, the gasket was venting case pressure into carb side of reed cage.
Mike
 
Sorry, Mike, I thought you were talking about a vent hose, not the passage. We checked all this includoing gaskets and vent passage after the problem 1st happened and before rebuilding, and then when we rebuilt again. Tank is exactly as it was when it ran for more a couple of seasons, or so, also checked fuel hose, replaced hose just in case, and I tried as much as possible not stopping engine by pulling spark plug cap, Jack. One thing I didn´t check is the KB06 pipe, and now that you mention that I think it is smoking too much through flex area, so might be clogged somewhere. I have another one so easy to check, though would that be big enough to plose 4,000 or more rpms? Tell you the truth I have Motoplat on most of my 2 cycle engines and never had the ignition or even coil gone bad. Maybe I have been lucky. I know, I know, you don´t trust Spanish stuff, lol. I´ll check carb, gaskets, reeds and pipe again. I am sure there is no rag inside header or exhaust. Clutch is engaging at same point it was engaging when running good, close to 10,000 and it has one race since last time it was completely rebuilt by Birky. Well, less than a race actually, lol. I´ll keep trying. In the stand doesn´t seem to rev much over those rpms either, though I didn´t want to rev up much without load.
 
Not dissing spanish stuff they are just very old. When they go through so many heat cycles and years of possible dry rot thing tend to not perform as intended. Remember when indoubt fresh is always best.jmo.
 
If your pipe is restricted or plugged it sure won't hit topend at all. This has happened to my dad before. Heated the pipe up with a torch to burn it out and then dropped it into a tub of water. All the castor build up came floating to the surface. Pipe was like new and engine ran beautiful after that. I have also seen paper towels and shop rags stuffed in the header get forgotten about (it happens) that will stop it up for sure maybe not completely but enough to cause a problem. Yours doesn't make a back firing sound does it?

Frankie
 
1fastyammy said:
If your pipe is restricted or plugged it sure won't hit topend at all. This has happened to my dad before. Heated the pipe up with a torch to burn it out and then dropped it into a tub of water. All the castor build up came floating to the surface. Pipe was like new and engine ran beautiful after that. I have also seen paper towels and shop rags stuffed in the header get forgotten about (it happens) that will stop it up for sure maybe not completely but enough to cause a problem. Yours doesn't make a back firing sound does it?

Frankie
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No, it doesn´t sound like backfiring. I am, gonna try my spare KB06 before trying other things. Thanks a lot for sharing your experience.
 
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