diagnosing a possible transmission issue (non FZ6)

[gnyce]

Throwing this out there to those mechanically-inclined as this is out of my depth/experience to-date. Short form, working on a project, a 1990 Yamaha FZR600R. Condition was unknown, but I liked the backstory and I love the look of these bikes, plus it was cheap. Have it turning over/running, but discovered a possible transmission issue. There is a knocking going on, slight in 1st gear, more in 2nd, very noticeable in 3rd. It has a new chain (installed before discovering this issue), and I just replaced the clutch friction plates and springs. This has improved 3rd gear - before the clutch plates, it was basically unusable - sounded like a steel ball in a spray-paint can - but now you can actually get into 3rd. Transmission access is a 'drop the engine/crack the case' operation. Shift cam and forks can be reached from underneath (through oil pan). Interestingly, the bike came with a 2nd engine - again, condition unknown - so maybe I try swapping and see.

Video illustrating here: any/all thoughts welcome.

 

[Gary in NJ]

I hear nothing unusual. An unloaded chain will always make that sound. It's the 1) chain rollers rolling against the face of the sprocket, and 2) chain slap from being unloaded. My intuition tell me if you get the bike off the stand and take out on the road, you will not hear that sound.

 

[gnyce]

I hear nothing unusual. An unloaded chain will always make that sound. It's the 1) chain rollers rolling against the face of the sprocket, and 2) chain slap from being unloaded. My intuition tell me if you get the bike off the stand and take out on the road, you will not hear that sound.

Thanks, did not know that re: unloaded chain. I've been reticient to take on the road as I don't yet have brakes in place. So just did now, and the issue with 3rd is still very much there.... rattles like crazy when shifted to 3rd and you apply any gas. Still leaves a question in my mind as to whether it is 3rd gear, or the shift-fork/other not fully seating it into 3rd, but - given that I have a 2nd engine, think I'll look to giving that a once over and if it appears OK, look to swap that in instead.

 

[TownsendsFJR1300]

I would take it for a slow safe ride, but as you noted, your going to have to get inside the box.

Re if it's a fork or gear, a bent/worn fork will usually result in not going into gear fully/popping out of gear-neither you have.

I suspect with noises, coming from all three gears, more probably not 3rd gear alone, but perhaps the shaft or side caged bearing failed..

Shouldn't be that hard to find once opened up.

Yamaha Motorcycle 1990 OEM Parts Diagram for TRANSMISSION | Partzilla.com

Buy OEM Parts for Yamaha Motorcycle 1990 TRANSMISSION Diagram

www.partzilla.com

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[gnyce]

Re if it's a fork or gear, a bent/worn fork will usually result in not going into gear fully/popping out of gear-neither you have.

I suspect with noises, coming from all three gears, more probably not 3rd gear alone, but perhaps the shaft or side caged bearing failed..

Yamaha Motorcycle 1990 OEM Parts Diagram for TRANSMISSION | Partzilla.com

Buy OEM Parts for Yamaha Motorcycle 1990 TRANSMISSION Diagram

www.partzilla.com

It doesn't pop out, but it _could_ be described as not going _into_ 3rd gear fully. I think 2nd gear is typically the problem with these models, but 1st/2nd and 4th seem fine, only 3rd demonstrates the problem - but you may well be correct, could be more going on than just 1 thing.

 

[gnyce]

Let's try this again. It's a poor recording, apologies - my phone was taped to the gas tank - but you can hear me speed up through first gear, continue with 2nd gear, and the rattling in 3rd gear. It does not seem to actually rattle in 3rd until you add just the tiniest amount of throttle.

WAV file - audio recording

This has gained additional significance, b/c my original plan of swapping to the 2nd engine is a non-starter as it turns out it has a broken engine mount, as well as a chunk out of the case near the starter clutch cover. So basically, I'm hoping that someone might have an inkling as to whether this is 3rd gear or shift-forks/other. As I've never torn an engine down before, my current thought is to practice on the broken-engine-mount engine (and maybe scavenge for parts)

 

[gnyce]

Re if it's a fork or gear, a bent/worn fork will usually result in not going into gear fully/popping out of gear-neither you have.

I suspect with noises, coming from all three gears, more probably not 3rd gear alone, but perhaps the shaft or side caged bearing failed..

Yamaha Motorcycle 1990 OEM Parts Diagram for TRANSMISSION | Partzilla.com

Buy OEM Parts for Yamaha Motorcycle 1990 TRANSMISSION Diagram

www.partzilla.com

.

More and more I'm suspecting you are right, @TownsendsFJR1300 - especially as I sense a slight grinding even when idling/in neutral.

 

[TownsendsFJR1300]

With a shop manual, lots of pic's and notes, you can get into that box. Use a parts diagram as well.

In your case, open up the parts engine first. You may need some special pullers but you'll find that out soon enough.

That 3rd gear noise is nasty. That won't be hard to find

 

[Gary in NJ]

Yeah, it sounds like you've got rocks in there. I agree with Scott, the second engine isn't of any use to you, so you might as well use it as a teacher. One thing is for sure, that engine isn't gonna get better on its own. Your choice is to replace it or repair it. Sell the bike would be unfortunate and paying someone to repair it probably doesn't make economic sense.

 

[gnyce]

Thanks guys - looks like I've got a bit of work ahead of me Got the bike + parts-engine for $300 so I'm not hugely underwater, just hoped I'd get luckier WRT the condition of the bike. If nothing else, it'll be an education.

 

[TownsendsFJR1300]

Thanks guys - looks like I've got a bit of work ahead of me Got the bike + parts-engine for $300 so I'm not hugely underwater, just hoped I'd get luckier WRT the condition of the bike. If nothing else, it'll be an education.

I would check on line for transmission parts availability at least BEFORE you open the original engine..

I'd open the old one up just cause!
Inspect that transmission assembly, know you have parts that are needed or are indeed available. before tearing the "good" engine..


Partzilla: https://www.partzilla.com/catalog/yamaha/motorcycle/1990/fzr600ra/transmission
shows many/most transmission parts not available.


.

 

[FinalImpact]

I suspect a bearing in the trans has let go. Once free of lube, a rough bearing will be very noisy. That said, the old chain jumps a bit like it has a kink. Is it a six speed box? what does 4th sound like? 4th is often 1:1 and can be more civil than the other gears. Splitting cases is not a big deal, hopefully you see something obvious...

 

[gnyce]

I suspect a bearing in the trans has let go. Once free of lube, a rough bearing will be very noisy. That said, the old chain jumps a bit like it has a kink. Is it a six speed box? what does 4th sound like? 4th is often 1:1 and can be more civil than the other gears. Splitting cases is not a big deal, hopefully you see something obvious...

The video indeed shows the old chain, and you are right it was kinked in a few places. Since been replaced. Yes, it is a 6-speed. 4th gear sounds just fine (as does 1st and 2nd). There is a slight grinding even in neutral, so yes a bearing could be involved as well. Hope to start this wknd...

 

[gnyce]

<Picking back up on a 1990 Yamaha FZR600, previous single-owner, 57k miles/>

One thing I found about the transmission grinding-noises later... the noise from the transmission did NOT happen while the bike was running on and its' side stand. But once you took it off the side stand and made it level (e.g. sitting on it), the grinding immediately began.
____

Picking back up on this project, some updates. It had languished in my garage and I'd done nothing with the engine, b/c 1) Covid, 2) college kids home, 3) got a dog, and 4) work.

- Finally called around, no shops really wanted to tackle this.... too old for a normal cycle shop, too new for a restoration place (and too much $)
- Replacement engines on Ebay were too much $ with no guarantee that they didnt' have issues as well
- Found a young guy on CL that was willing to tackle this, so... took a chance with him (he normally just does 2-cycle engine rebuilds)
- End result is that the engine is now rebuilt (it wasn't too bad a shape apparently); gears were a little loose, no obvious issues with the trans; there _were_ metal bits in the oil pan, and he found an internal bolt mount/fixture (upper <--> lower case) that was disintegrating, the suspected cause of said metal bits... so he used a 2nd engine I had obtained (in the same sale, that one was not usable as-it-was) and used the lower half of the case + the transmission from it. I picked up the bike 2 weeks ago, and started in on the remaining issues. It ran, but was still a bit rough (but shifting through all gears worked with no issue!). Finally!!

And then...

It started running roughly, with minimal power, and then stopped running/could not get it started. I thought I caused this, in my aim to set the carb back to factory/baseline settings, or some dumb mistake - but even starter fluid was insufficient to get it going. Finally tracked it down to weak spark (there _was_ spark, but it was yellow/white). Out comes the multimeter, with which I am only vaguely familiar. Plugs are mostly new, plug caps tested ok, same with ignition coils, no reason to suspect neutral/side stand switches, and no different behavior with two different CDIs. Finally figured it was the Stator - and in showing my neighbor my neophyte multimeter readings, he points to the Stator harness where it has clearly been cut and said "there is your problem". Sure enough, the harness/wire was missing a bracket (it is shown in picture) to keep it away from the rotor assembly, and it was gradually sliced through, which explains why it slowly went bad from running 'ok'.

Anyway, I now have a way forward again. Nothing worse than thinking you have a self-inflicted wound. Requisite pictures....



(headers are not polished, but ceramic-coated)

 

[Motogiro]

Very nice! That bike also has cold air induction!

 

[Gary in NJ]

Good find on the cut stator wires. That can be a tricky one to isolate, potentially costing you a new battery, regulator/rectifyer and eventually a new stator (with uncut wires) - and a lot of headaches along the way.

 

[gnyce]

new stator installed. Some self-inflicted carb wounds in my attempts to get back to a factory base-profile, but got her fired up today and did a 15-mile loop. Some rough spots, needs fine-tuning (uneven at 3k, slight hesitation on throttle blip), but feels decently solid and pulls all the way through the revs. It seems that I get some carb experience under my belt, become over-confident, and get taken down a few pegs on the next encounter. Humbling. But what a lovely day to be on the road!

https://photos.app.goo.gl/yqptY3NyhztHBEVw8

 

[Gary in NJ]

Excellent! Sounds mean.