Clutch, or something more serious?

[xwhatsit]

Hihi,

My clutch isn't very nice. It's always a struggle to set it up between slipping and dragging (in terms of cable slack), probably because of the excessive abuse it gets at the Traffic Light GP (compounded by the much taller geared sprockets I've put in).

Anyhow, it's started doing a new trick lately. Wind it up in first gear away from the lights, and a few thousand RPM before redline, suddenly the engine screams and I just about pitch forward over the handlebars. It's exactly like a gear jumping out; except, as soon as I back off on the throttle, it goes back to normal. It certainly doesn't go into neutral or anything (as far as I can tell with my left foot).

Now, that would seem to be a slipping clutch. But I'm a little confused. Limited prior experience with clutch slipping has been of a gentle sort of CVT scooter effect. This is a violent let-go; one moment it's holding on, next moment all hell is breaking loose. Also, why is it happening in first gear? Isn't this where the least stress is on the transmission? Wouldn't slipping like that happen in fourth or top as I'm winding it out on the motorway?

Of course, my curiosity will be satisfied whenever I have a spare moment to replace the clutch bits, but I'm rather anxious about this being a gearbox problem. I like to understand what's going on, rather than just throwing parts at the bike.

[CookMySock]

I like to understand what's going on, rather than just throwing parts at the bike.

hrm that pretty much sums up a full 50% of servicing anything 'mfraid dood. Many times we have no idea what the problem was.

DB

[vifferman]

.... a few thousand RPM before redline

That would be when the turbo and Vtec kick in at the same time?
Don't you have it back-to-front - isn't first gear where the engine's doing the most revs relative to the wheels, so there's the most strain on the clutch? :spudwhat:
It sounds Eggs Zachary like the gearbox shifting into neutral or false neutral to me, but if it's not that, and is the clutch, then it's either worn / glazed plates, or tired springs (the most usual problem).

[NOMIS]

My hornet does this if i load it up to hard taking off readlight gp style. But it usually not as bad as your sounds and normally when i change into 2nd gear it will go then loose 2nd back to neautral,
quite embarrasing hitting redline ringing the nut off it.

[xwhatsit]

It sounds Eggs Zachary like the gearbox shifting into neutral or false neutral to me, but if it's not that, and is the clutch, then it's either worn / glazed plates, or tired springs (the most usual problem).

Yeah, I know it does sound like that, but it's different. That happens in second gear sometimes if you're not firm when selecting it (classic 250RS problem), but the difference is, is that it jumps out of gear and stays out of gear. This `slips' or jumps out or whatever in first, but then when I back off it engages again and everything's back to normal.

EDIT: And oh yes, it only happens when hot.

[Magua]

http://www.davidsilverspares.co.uk/p...res/part_2582/ _b

[vifferman]

Yeah, I know it does sound like that, but it's different. That happens in second gear sometimes if you're not firm when selecting it (classic 250RS problem)

No, classic Honda problem.
I've owned 7? 8? Hondas now, and every one has ended up with a crap gearbox. Yeah, I know I'm a serial gearbox wrecker, but even so, Honda gearboxes aren't great. The VFR had the best gearbox of any Honda I'd ridden (till I'd thrashed it a bit), and it's even better since I put a Factory Pro Evo Star shifter kit in it, innit? Now it generally behaves, except when the chains too loose/ tight / dirty or I'm especially sloppy on gearchanges.

[CookMySock]

zounds like a worn gearbag part, like a selector or a dog.

DB

[Ixion]

I'd say a worn selector. The torque load on the gear under heavy acceleration is enough to push the dog back against the selector fork. When you button off the fork reengages it.(Actually, it's probably wear in the snail groove and pin so that the fork can be pushed back a bit up the "ramp'. It's sort of hard to explain)

[xwhatsit]

Ah, feck.

Oh well, I've got a 6-speed gearbox sitting in the garage, and two other mangled engines. I'm sure I can put something together eventually before it all turns to custard. Splitting the cases on my existing engine is not something I am relishing.

Hmmph. Wear in the selector drum seems funny, how fast do those things rotate at the end of the day? 1 rpm?

[xwhatsit]

Oh, I should probably ask as well, if it is such a gearbox issue, am I causing any more damage by riding it like this (just not giving it heaps in first)? I drained the oil out a couple of days ago and can't recall seeing any metal bits floating around...?

[Ixion]

Ah, feck.

Oh well, I've got a 6-speed gearbox sitting in the garage, and two other mangled engines. I'm sure I can put something together eventually before it all turns to custard. Splitting the cases on my existing engine is not something I am relishing.

Hmmph. Wear in the selector drum seems funny, how fast do those things rotate at the end of the day? 1 rpm?

Only rotate when you change gear. But it's quite heavily loaded, depending on how delicate you are with the clutch. Remember, the bike is how many years old?

[xwhatsit]

Only rotate when you change gear.

My point -- then again, for its quarter-century lifespan it has done a lot of communting. *Bang* first gear, up into second -- 20 seconds later, red light, *bang* down into first and click into neutral.

Dropping those aluminium shavings in the sump from the cam sprocket affair probably didn't help, either

Maybe changing down to standard sprocket ratio will help alleviate the symptoms somewhat; shorter first gear means less stress on the transmission (@Vifferman -- my theory is that it's easiest for the engine to accelerate/do wheelies/spin rear wheel in lower gears, so there's less stress, whereas in top gear the engine is struggling to push against the rear wheel to accelerate. Dunno).

Monster 6-speed bored-out lumpy-cam CB275RS time.

[Ixion]

It could also be wear on the little hooky thing that turns the selector drum. So it's not *quite* indexing. In which case you might be able to fettle it. The hooky thing is often accessible without splitting the cases (though that's not really a big job on a single)

[avgas]

how tight are your springs - i had a similar issue with one of the GB's. Drained oil and went to pull clutch plates out and noticed that one of the bolts holding the spring was a bit loose.