knocking in 4th gear

[jfinn]

I bought an 85 FJ1100 that was off the road for about 7 years. After going thru a clean up and rebuild of the brakes and clutch cyl., carbs, and tuneup, I got it running. I put the bike thru a couple of warm up /cooling cycles to get things moving again. Finally took it  for a shake down ride around the neighborhood. When I shifted into 4th and 5th there was a loud knocking. I took the chain off and ran the bike thru the gears on the center stand . The knock was mostly gone. I checked the chain and found it was missing about 3-4 links - too tight. I replaced it and both sprockets.

After running the bike around a little more - the knock is gone in 5th but still there in 4th. The local dealer said 4th is blown. I'm not sure I believe that. It shifts very smooth into 4th, out of 4th to 5th and back down again. The knock can be heard (very light) while the bike is in gear but the clutch is in. I can power thru 4th with no problems other than the knocking.

I think it may be the shift fork or something not retracting between shifts. Unfortunately, I am not that knowledgeable  with the inner workings. I've put about 600 miles on and the noise is still going strong. I'm going to put Klotz synthetic racing oil in to see if that may help. Most of the time I just skip over 4th and go into 5th.

Any Ideas?   

   

[racerman_27410]

pull the header pipe off the front of the engine and check and see if the inner walls of the header are all rusted out and broken...... its pretty common on the early model FJ's and i have heard some of the noises firsthand.... it does sound fatal but it's not.


never have i heard even one time of 4th gear going out on a FJ..... for any reason.


KOokaloo!

Frank

[jfinn]

Frank,

I've already had the headers off and they were fine. 2nd gear was a problem on this bike but I found a work order from a repair shop and that was fixed in the early 90's.

I still think it is something stuck in the wrong place - the trans is too smooth otherwise.


John

[ren-dog]

jfinn,

Knocking noises in gearboxes are not caused by blown gears, if the gear was missing teeth
there would be a loud grinding and crunching and much vibration obvious through the chain drive.
BUT 
Knocking noises in a gearbox are typical of worn bearings and bushes OR bent shafts.
So the end result will be the same unfortunately. Gearbox out.

Now let me further add that I have never seen the inside of an FJ's box,
nor have any experience repairing motorbikes. If however my theory is
to be proven correct I would need to know if 4th and 5th gear are on the
same shaft? A parts diagram for your specific model would tell us this.

If you have access to a dial gauge you can set it on the gearbox output
shaft, i.e very close to the drive sprocket will do. Then rotate the rear wheel
whilst in 4th/5th gear. Also check to see if there is any slop in the output
shaft bearing by levering the sprocket back and forth.

Hope this helps.
Cheers,
ren-dog