Losing power at full trottle

[Groove]

@Nightcruiser - great posts!! I hope this helps KKalan with his issue. I know I'll be referring to this again in the future should I have any trouble with the carb.

I also agree with Crassius about running in the sweet spot range. I call it the groove LOL. Too slow it they're herky jerky. Too fast and your RPMs get too high which seems like it could be problematic..

 

[kkalan]

Found problem! Small crack in the intake pipe. Jb weld and it runs great! Thanks for the help!

 

[nightcruiser]

Found problem! Small crack in the intake pipe. Jb weld and it runs great! Thanks for the help!

Congrats on nailing down the problem, happy riding.....

 

[leewayne66]

my 66 raw motor always 4 strokes at hi speed unless i run a .68 jet and no air filter. carb is level, hi comp head, jag cdi, reed kit and expansion chamber. i tried everything. dont know wat else to do.any ideas??? plz hlp

 

[nightcruiser]

my 66 raw motor always 4 strokes at hi speed unless i run a .68 jet and no air filter. carb is level, hi comp head, jag cdi, reed kit and expansion chamber. i tried everything. dont know wat else to do.any ideas??? plz hlp

Do a plug chop (with proper air filter in place) to determine if the 4-stroking is caused by running lean or rich? (prob rich) Once you decide what the condition is that is causing the the bog at WOT then some possible corrective measures would be:

Adjust float: set to hold more fuel in the bowl to richen - set to hold less fuel for leaner. I mention this first because the float can effect your mix quite a bit in my experience, it's an easy adjustment, and it costs nothing to do. In a lot of cases you can get the WOT mix where you need it with the float adjustment alone, then set the needle adjustment for best mid throttle response and your done...

Change jet size: smaller for leaner - bigger for more rich

Change air filter flow: Allow more/easier airflow for leaner - create more restricted/less air flow for richer

Change Exhaust: Same as air filter...

If the problem you have is carb related these are the common ways to correct it...

You could have other things going on though, like foamed fuel in your line, gas cap not venting, spark plug cap vibrating loose just to name a few...

Happy tinkering and good luck....

 

[leewayne66]

im going to try those. gotta hook up my kill switch to chop it. the float bowl sounds real interesting. when you said change exaughst same as air filter? i heard someone say they drilled holes in it to hlp with 4 strokin. if you can look at my pics of my bike and tell me wat you think of the exaughst with the expansion chamber. http://www.facebook.com/#!/lee.wayne.543792

 

[Toadmund]

my 66 raw motor always 4 strokes at hi speed unless i run a .68 jet and no air filter. carb is level, hi comp head, jag cdi, reed kit and expansion chamber. i tried everything. dont know wat else to do.any ideas??? plz hlp

Try a 0.65mm jet and put on your air filter for crying out loud!
With an air filter on you will suck more gas making it 4 stroke, especially if it's dirty.

 

[leewayne66]

they dont make one that small for the jnm performace carb. i was thinking of trying the cns racing carb where i can adjust air/fuel mix or a deltoro. also i have to make a custom air filter for i dont have enough clerance for one to fit. i heard someone say that they drilled holes in the end of their baffle to hlp get better air mix. is this true??

 

[leewayne66]

also my expansion chamber is the bannana shape but at the end of a long pipe. it is 14" from exaughst port to start of expansion chamber. should it be closer? i read that it has to be a min of 6" no more than 14" to start of expansion chamber

 

[Toadmund]

they dont make one that small for the jnm performace carb. i was thinking of trying the cns racing carb where i can adjust air/fuel mix or a deltoro. also i have to make a custom air filter for i dont have enough clerance for one to fit. i heard someone say that they drilled holes in the end of their baffle to hlp get better air mix. is this true??

I filled and drilled mine myself.
Fill the jet with lead solder (if you can get lead solder) and get some micro drill bits and try drilling to a 0.65mm hole.
Use the search and look up 'soldering jets'

 

[CTripps]

also i have to make a custom air filter for i dont have enough clerance for one to fit.

Many have come up with off-set intake manifolds to get around that problem. The closest I have to that right now is on my cruiser, I have to take the air filter off the carb to install or remove the carb. Taking off the filter gives me the extra 3/8" or so I need between motor and frame to get the carb off the manifold.