Bike stumbles/hesitates under WOT in 2nd only

[PeteGLH]

Hey all,

Title says it all.  Under WOT,  in second gear,  bike pulls to 4500,  then it stumbles,  picks up again,  stumbles again towards 7000 then picks back up..... Seems strange.  I don't know much,  but I know it can't be carb/fuel related as it runs fine under WOT in all the other gears.   

Any ideas to what could be the culprit of this issue?

[Pat Conlon]

Pete, you and I have '84's.  I have Bad news. What you are describing is the dreaded 2nd gear issue, common on early FJ's.
The shifting forks on the early FJ's are weak and bend, causing 2nd gear to separate under load.
You can short shift around the problem but ultimately you will need to pull the motor and replace the shifting forks with the late model FJ forks.

***Do not continue to abuse your tranny or you will cause further damage***   If you have to ride your bike, short shift around 2nd gear..

If you had a carb issue it would manifest itself in the other gears. Search in the files section we have a primer on how and what you need to fix 2nd gear.

Cheers!   Pat

[edit] Here ya go: http://www.fjowners.com/index.php?topic=666.0     How appropriate: topic 666

[PeteGLH]

Thanks for the input Pat.   I will be pulling the engine after the season so this will be part of the fixing up.   I knew it had to be something major with the tranny....  Any chance I will damage any other gears if I short shift through second?   I don't expect to be running much WOT in 5th so...

Riding season in Quebec is short,  would hate to lose the bike for a week or two fixing this up... 

[Pat Conlon]

You will be ok in the other gears, just take it easy with second gear. When riding best to bypass 2nd entirely, or at least short shift around it. Pat

[carsick]

WOT in second gear,  bike pulls to 4500,  then it stumbles,  picks up again,  stumbles again towards 7000 then picks back up

The second gear dilemma feels like a STUMBLE? I thought it was a kick out and scream to rev limit kinda thing, with occasional vicious jolts of re-engagement. Please enlighten me, any noises you can make or pantomime of what you did when this happened as you were passing a tractor trailer would be helpful also.

[Pat Conlon]

WOT in second gear,  bike pulls to 4500,  then it stumbles,  picks up again,  stumbles again towards 7000 then picks back up

The second gear dilemma feels like a STUMBLE? I thought it was a kick out and scream to rev limit kinda thing, with occasional vicious jolts of re-engagement. .

Nope, not for me. My experience was that there was little or moderate over reving.....Nothing drastic like a kick out and scream to redline,  just a hard stumble, which would happen multiple times under load.
I could tell that it was the tranny, no question. It only happened in 2nd gear under load.

[racerman_27410]

my 2nd gear issue felt (to me) at WFO like the chain was skipping teeth on the sprocket.

mine never got really bad as i tore into the engine and fixed it right away... the dogs and windows of the 2/5 gearset really didnt look that bad but the shift fork was definitely bent.

i went ahead and updated all the shift forks and the 2/5 gearset as i had already pre ordered the parts and had them undercut before starting the job.


KOokaloo!

[Pat Conlon]

my 2nd gear issue felt (to me) at WFO like the chain was skipping teeth on the sprocket.

Yea Frank, that's a good description.

[andyb]

my 2nd gear issue felt (to me) at WFO like the chain was skipping teeth on the sprocket.

Exactly what first feels like when it does it also.  Really a bastard to troubleshoot, I thought I had chain tension problems