Fj1100 jumps in first at 5k

[Fj1100 Rebuild project]

I got my fj running tonight, found out that it has the second gear pop out issue which is a bit of a bummer but I'll just skip into third until I can afford to get it fixed, one thing I noticed is in first gear around 5k rpm the bike "jumps" at least that's the best way to describe it, at first I thought it was popping out of gear but every time I roll back onto throttle it happily accelerates. Any thoughts? Every time I feel it I immediately get off throttle and the bike has sat for who knows how many years, this is the first 20 miles I've put on the bike so I was expecting some gremlins to pop up. Also anyone know of a cheap and easy fix that might allow me to use second temporarily until it gets fixed?

[Motofun]

Sorry, there is no cheap easy fix for the 2nd gear woes.  You can slow down the shift into 2nd and perhaps that may help but unlikely.  If the dogs are too badly worn it will refuse to stay engaged under heavy abuse.  I assume you are saying that at 5k rpm as you steadily accelerate the bike experiences a positive surge....hmmmm...all things being equal the only thing that makes sense to me is a fueling issue.  I'd start with something simple like lube all the throttle cables but I'm just guessing.  Does this only happen in 1st?

[melloncollie]

At a glance it sounds like first gear is beginning the same second gear issue.  Does it feel like what's described in this post?  https://fjowners.com/index.php?topic=17735.msg178981#msg178981

I I've just swapped out my motor in my 84 FJ for an 89 1200, because of the second gear issue. It would pop out and back in with just spirited riding around town. It was like hitting g a bump and having the rear wheel pop in the air. And before anyone says that I was pushing it hard. It would happen at half throttle at about 5000rpm. Obviously it was a lot worse in the tight twisty stuff.
I had installed one of Randy's Detent kits, which helped for a while and installed new clutch plates.
I am told that from about the 88 FJ on, Yamaha had corrected the main culprit (the shift yokes) with re engineered item, the same as in the XJR1300.

Mark

Mine (1984 1100) does it a lot if I'm accelerating hard up a grade. What it does is hammer on and off, quickly and repeatedly until I back off the throttle or better, change out of 2nd gear.

Are you sure the gears are the prob? It doesn't sound so.... But if it is only in second....hm.... My experience with manual transmissions on cars and motorcycles is that if it pops out - it pops out. No 'on and off'.

Charlie's description is the classic description of the second gear problem.  The engagement tabs and mating windows get slightly rounded off (due to wear from improper engagement and weak shifts).

Then instead of pulling the two gears together, like they would when properly undercut, they actually push the two gears apart under load.  This causes the two gears to separate and disengage thus reducing the load momentarily which allows the gears to come back together.  If you keep the load on, this cycle repeats causing the engagement/disengagement studder that Charlie described.

[fj1289]

Yes - first gear can develop the "second gear issue" too.  RPM sells undercut transmissions with 1st, 2nd, and 3rd gears undercut.  The problem isn't just with FJ's - most of the motorcycles from the era suffered from the issue.  The size and mass of the lower gears make them most likely to develop the issues.  And I'd course, as the gears force themselves apart, the shift forks get bent out of shape - which makes the problem worse - and is part of the solution. 

[Bozo]

I do suspect a gear issue especially FJ1100 but on my FJ1200 I had a miss once in a blue moon at full revs 7 to 9,000. It felt like the chain skipped on the sprocket. I knew the gearbox was in top condition (I had it apart not long before) eventually it was more consistent until once day I couldn't rev it above 3000rpm, yes it turned out to be my CDI. After replacing unit the bike was 100%.

[fj1289]

So true when it comes to figuring out issues like these - don't just focus on one thing - gotta take in the whole picture and work through the possibilities!

Was that the stock CDI?