not much power till 4000rpm

[wjw11teen]

so i have about 400 miles on her now since i did extensive carb re build valve adj. all fluids etc.etc.

took it for a good hard thrashing afew days ago...shifted around 7000 to 7500

held it WFO for a god rip a couple times...only pulled up to 7400 in top cog at wide open

now it doesnt seem to make much power till around 4000 then she will pull pretty good...

have not done the petcocks or octo.yet...seems kinda sluggish down low..also kinda sounds like there is an exaust leak
but i only really hear it well with my helmet on...tightened the header bolts,a couple loose but not bad

any thoughts? mabey i ran her to hard?

[TopCatGr58]

Hey there,

I quickly reviewed your past threads, but it will be helpful for the other members if you would provide a recap of what you've done to the bike/engine prior to experiencing your recent problem. Aside from the valve and carb work, I think you also did the Dremel fix?

Okay, you found some header nuts slightly loose, retightened. I run mine to 7500 often, no problem there that I can see, doubtful that you would have floated a valve. With your carb work, did you put INLINE fuel filters on it? The In-Tank petcock filters are not good enough. Having power after 4k rpm sounds like the mains are still flowing, but your pilot circuit may have gotten partially clogged...possibly from debris/rust stirred up in the tank after your run?? I think you have the 81, they are less likely to have the PU coil wire problems. Ensure you're still hitting on all 4...all 4 pipes sizzle when spritzed with water.

T.C.

[wjw11teen]

good call on more info TC

i have also had the engine apart including cyl

i installed some new valves and a new cam chain

i did some mild clean up work in the int.and ex. ports but not much

bike has been running great till this little ass whoopin i put on it

today my son (who is pretty knowledgable for 12 told me it was popping and sputtering on decell...but not whil accel ..It had about a 1/4 tank at that time so i filled it with 91 oct. and the poping seemed to go away and it had better low end grunt

so im thinking its in the fuel delivery system..and possible needs to have a good carb cleaning done again...

thoughts and input is always appreciated

[jjz28]

Like tc mentioned, you may have you pilot circuit clogged up a little. That is you low end and then at about 3500 I believe, it kicks into the mains.

[motoman]

good call on more info TC

i have also had the engine apart including cyl

i installed some new valves and a new cam chain

i did some mild clean up work in the int.and ex. ports but not much

bike has been running great till this little ass whoopin i put on it

today my son (who is pretty knowledgable for 12 told me it was popping and sputtering on decell...but not whil accel ..It had about a 1/4 tank at that time so i filled it with 91 oct. and the poping seemed to go away and it had better low end grunt

so im thinking its in the fuel delivery system..and possible needs to have a good carb cleaning done again...

thoughts and input is always appreciated

A third cleaning may do it(triple clean). Idle mix likely too lean with the popping on decel. Bench set those bout 3 1/3 turns out for starters on the later carbs. Of course, your still gonna have to do an actual sync to dial it in. The later model advance DOES and can result in a broken pic-up wire......usually the white one. A visual of those does NOT work. Have to stretch every inch to find broken internally. Apologize for running this all together.........doing on phone sucks.

[motoman]

FWIW, the later 4RO systems, even tho mechanical advance is through TCI, the vacuum advance rotates the same amount(make sure it rotates freely)as the early models. They are separate of each other on the early models. In other words, the early 2h7's and 4RO's vacuum advance rotate the same distance. The only change made between the two associated with the pic-up wires was the loom holder location which gave the later 4RO wires a bit more free play, but still no help for the constant movement of the vacuum advance plate.