Crunching gears

[UK Pete]

What makes a bike crunch when you put it in first gear?
When i am sitting at lights with other bikes then every one senses the lights are about to change , all you here is a load of almighty crunching where people are selecting first gear.
I think Honda is the worst just by way of observation and that any honda i own does it
Having just got my F2 back together and giving it a few runs around the block i have noticed with mine a big crunch when selecting first, its probably the worst i have had on a bike and it is the same for my K1 both of them do it bad, the clutch is working really good on the F2 no drag whatsoever so is it just bad design, i find my Kawasaki's dont do it so much but my Yamaha FZ1 does but only when hot.

OH yes the F2 is on its way to the MOT station in an hours time , fingers crossed
Pete

[SteveD CB500K0]

Motorcycle gearboxes don't have synchromesh.

[Spitfire]

Clutch adjustment maybe ?

Den

[florence]

I agree with Steve about the syncromesh.  When your bike is stationary the gears you are bringing together are not running at the same speed as one another.  The only way you could eliminate the crunch would be on a rolling start when you would have a chance at matching the engine speed with the speed of the wheels.  I have been forced to do this on a number of occasions when my clutch cable has broken.  With practice, you will find that, providing you get the revs right, it is not necessay to use a clutch at all on any vehicle as long as you do not need to do a hill start!

[SteveD CB500K0]

Modern bikes do it too.  It doesn't matter how expensive they are!

[kaceyk2]

one thing that tends to exagerate the crunch is a too loose chain, but I bet yours is fine....
Florence, you reminded me of when I was coming home from town in the seventies in a mini...the clutch slave burst..I had a mate with me...we crunched through the gears no probs..untill..the traffic lights were on red.. oh no oh no.... we jumped out, pushed the car allong with the motor running in neutral with the idea of building up some speed to engage second gear... when we got some speeed up, i jumped in and shouted at him to do the same....I engaged second, and tried to go as slow as possible without stalling , lurch, creep, lurch creep, he nearly got in about eight times before he actually did and thought I was doing it on purpose... we got home without any more red lights, he said he couldnt have done it again....red faced and out of breath...funny... it is easier on a bike!!!

[K2-K6]

Bikes are always dog engagement (almost without exception) and would rely on the clutch totally releasing to stop any rotation from the motor when stationary, which is hard to do with an oil bath clutch that normally drags a bit with the oil between the plates.

If they didn't drag at all you'd have have more difficulty getting into gear as occasionally you get them dog to dog and have to roll it along or let the clutch out a bit to rotate the gear shafts (like when you try to change gear without the motor running).

The car one (broken clutch) you solve by starting the motor with it in first gear, bit of throttle and away you go!! done it many times in mainly minis. (no not wearing a skirt before you ask).

[kaceyk2]

You got me there..why would I ask if you was weraing a skirt? I forgot to mention, my mini had er two or three teeth missing off the ring gear on the flywheel...and for some (probably explainable scientific reason that passed me by) reason it used to stop in the "no teeth-to connect to starter motor position" about 50/50 chance when it stalled or was switched off, used to have to open door, put it into second , rock it,to where the teeth were at and try again..... at traffic lights this usually meant the person behind me had lost patience and was trying to pull out to overtake and miss me door/leg... It allways puzzled me how often it stopped in this position, I mean there was loads of teeth where it could have stopped?

[Bryanj]

A 4 pot will always stop when 1 of the pistons is on compression so in 1 of 4 places

[p@ul]

Good luck with the MOT Pete.........

Just a quick note on the f2 gearbox, when i test rode the bike i bought last week i was surprised how slick the gearbox was even into 1st gear there was no sign of crunching at all. I just assumed this was mormal as i've heard nothing different about these bikes..... Gues i've just dropped lucky !!

The R1 however is very different story, a shocking gearbox 

[UK Pete]

Hi Paul yes the bike went straight through the MOT yesterday, as for the crunching gears i suppose its more of a clonk that all bikes seem to have , my FZ1 is very similar to the R1 and its almost silent when selecting gears from cold, but as soon as its warmed up it clonks a goodun
Pete

[K2-K6]

Speaking just for the F2, if you take almost all of the slack out of the adjust pivot cam before putting the cable onto it then it should end up about 7 to 8 o'clock-ish and release the plates well which is what stops the crunch.

If the operation lever passes too far toward the cable entrance position then the tension at the hand lever rises at the end of it's travel and makes it hard to pull the clutch all the way in if that makes sense.

If the clutch plates are not really flat then it will be hard to stopp it dragging anyway and hence crunching.

If you go too far with taking out slack then you risk making it slip under high load.

[Seamus]

Must confess that all my bikes have done that, Everything from the Blades to the triple, to the SP and the old CB's. Sometimes selecting second before 1st helps.