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Discussion Starter · #1 · (Edited)
Hi,

first off, apologies for the title, but 'tonk' is about the best I can do to describe it, sometimes it is closer to 'toink', but hey it is annoying whatever it is. So what is it.....

It happens when I pull away, but not every time. I can't predict what causes it. Sometimes really gentle gettaways, slipping the clutch causes it, and sometimes not. It very occassionally happens when going from braking to accellerating.

I get a 'tonk' that feels like it is coming from the back bottom of the engine area. It is sort of a metallic sound as though something is taking up and then hitting a stop. Occassionally it is slightly less muffled and comes across as a slightly more musical toink.

It doesn't happen on any other shift, up or down, clutchless or otherwise, but only on take up either from pulling away, or going from braking to accelleration.

I can sort of feel it in the footpegs, and if it doesn't happen I seems to manifest itself as a roughness in the transmission of power.

So I have started investigating..

1. My bugbear, the rear brake carrier. The rear brake appears to be binding very slightly and this can cause a slight click as the plate rotates onto and off the bolt stop that exists, but I don't think it is that. If definitely has the sound of inside a casing.

2. Cush rubbers. Not sure how to check this - advice please

3. Gearbox output sprocket loose - Seen some scary threads about this, but nope on nice and tight with the tab bent over.

4. Clutch - Gerry, my friendly tech at the dealers suggested that one of the spring washers in the back of the clutch to do with rattle and backlash may have broken (apparently there have been cases), so I have just finished stripping out the clutch basket and everything seems to be in order, although I have yet to go through each plate in detail. No broken bits, but my first cause for concern.... with the box in first, the backlash in the gearbox between rotating the inner basket and the rear wheel moving is 1/5 of a rotation from freeplay take-up rotating anti-clockwise, to freeplay ending rotating clockwise (hope that makes sense, although most out there will understand backlash anyway). Is this normal? I can't seem to find an explaination in this for the 'tonk' though.

4a. Wrong clutch - okay, so this is a Daytona motor in an ST. How do I check that when it was installed, it has Daytona plates and springs? Are they different? I would guess that the plates should be the same, but I would assume to pass the greater power, that the springs would be stronger. All my springs had white paint lines down one side. Could it be the clutch slipping on take up?

5. Gearbox - Haven't even contemplated this yet. Could there be something giving in the relationship of the two shafts causing them to move under load (damaged bearing, worn casing etc)?

Other things that I might consider are...

1. Forks for wear and slack
2. Headstock free play
3. Front brake calliper mountings

Any help would be hugely appreciated as this is seriously getting in the way of riding, and panel spraying!

Puzzled!

Rexx
 

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For the cush rubbers, put your hand on the hub while you move the wheel slowly against the chain in both directions. There should be no movement.

This sounds weird, but try spraying some lube on the rear shock lower mount and dogbone swivel.

My bike had a 'pop-poppop' feeling to it when I rolled off a stop. Turns out it was the lower shcok mount sticking.
 

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Rexx

just as a note I replaced my cush drive rubbers at around 55,000kms.

Bare in mind that mine get a hammering though and you could use DEcosse's dog year theory on my mileage!:D

DaveM
 

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Discussion Starter · #6 ·
Some Progress

Hi Folks,

I had a quick firkle (old Engineering term, probably imperial rather than metric!).

the chain is only 6k miles old, and in good condition (thank you Mr Scottoiler).

As far as I can tell, there is no play in the cush rubbers, the 1/5 revolution is solely in the gearbox. It would be nice to confirm that this is normal, however, I think I have identified the culprit...

The inner clutch basket is solid, but I can grasp the fingers of the outer clutch basket and wiggle it up and down by about 1-1.5mm, making it click, watching the drive gear move behind it as well. I think this is my 'tonk' as the two baskets come in to alignment and the friction plates come together.

So looking at the schematics, it would appear that there are at least 2, if not 3 bearings in there.

Any ideas which is likely to be the culprit, and how hard is it going to be to replace them?

Rexx
 

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Discussion Starter · #8 ·
Fetish

I just think you have a rubber fetish... cush rubber, tyre rubber... all the same to you.... just an excuse to abuse it! :D

Rexx
 

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Discussion Starter · #10 ·
DaveM

You certainly do!!!

back on thread, I've just been to the dealers to get the gaskets, and on talking it through with Gerry, he is convinced that one of the springs that take up the drive in the backplate of the inner basket has broken. In which case it is £300 OUCH!! :(

Rexx
 

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Discussion Starter · #11 · (Edited)
More Firkling

Okay,

so I have done some more rummaging around the forum (using Google.co.uk to find things!) and I've taken the two clutch baskets off.

What have I found...

other posters on this forum have found that the clutch basket can be rocked on its roller bearing.

all the springs in the back of the outer basket seem to be present and correct, although two are shorter than the rest.



Judging by the spring wire thickness, length and colour coding, there appear to be three strengths of spring in there...

4x green - thinnest and longest (for normal load take up?)

1x blue - thicker and slightly shorter than the space it occupies (assistance when the greens are compressed?)

1x red - thickest and shortest (the final buffer?)

So it doesn't appear that the basket is faulty when moving on its bearing.

The springs seem fine.

The input shaft doesn't float or move.

So other than putting it back together, where do I look now?
Remove the 19t sprocket and wiggle the output shaft?

I'm Stumped

Rexx
 

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Discussion Starter · #12 · (Edited)
I have a nasty suspicion...

Okay, so a quick update..

I've

stripped the clutch
I've removed the output sprocket
I've adjusted the chain tension
I've checked freeplay in drivetrain

none of those has changed anything or found any problems

I can limit the time it happens to 1st and second. Not neccessarily on initial clutch take up, but certainly on putting some good drive through. I can do it in second by lifting off at reasonable revs, waiting til the bike has slowed and then opening up again.

When it does it, it coincides with a change that is baulky, either into 1st, or 1st to second. The remaining gears are easier, but sometimes it feels as though the gearbox is still transmitting power when midway through switching cogs.

So I am thinking that I have damaged a dog on the 1st/2nd cluster which is engaging enough to transmit drive even after the clutch is released, but then subsequently finishes meshing. It doesn't disengage cleanly each time, and it makes changing through the other gears when not fully disengaged difficult because it is still transmitting power!!

Does this sound like a solid theory?

How difficult is it to get into the gearbox?

Rexx
 

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Discussion Starter · #14 ·
Gearbox link

thanks OnD,

I had followed that link some time ago, but couldn't find it now that I needed it. So really useful. I'm getting very close to choosing to do this myself!

Rexx
 

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Gee Rexxy you and Kit have conspired together and run over a bus full of Chinamen! You've had some sh1tty luck lately :(

Good post OnD. Very interesting and easy for a simple soul like me to understand. Hengineering always impresses me (or is that baffles me) as to how these things work and we just take them for granted.

Good luck with it all Rexx. Very interesting thread and I would love to be there helping. Your summer is coming soon isn't it? I come over for that day and assist. :D I can bring the bairns. :)
 

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Discussion Starter · #16 ·
Bad luck?

Okay I'll bite...

I reckon it's going to take me probably a couple of weeks to do this, evenings and weekends, and plenty of sphincter resting time, so I'm sorry, but our spare room is full, and as I have told you before, I'm allergic to children!!!

Thanks for the 'selfless offer' though!

Why do you think I've had a run of bad luck?

Rexx
 

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Your engine rebuild would have been a challenge for me. :(

I guess when I look at "having" to work on my vehicles instead of wanting to/tinkering/normal services as an inconvenience nowadays. That's all. :)
 
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