South West Bikers | Motorcycle Forum

Hi all

I am reasonably new to biking and i want someone to tell me what is going on.

My bike is a honda cbr125r. At around 70mph the speed will be constant at full throttle on a constant incline. It is in top gear and the clutch is not pressed but yet my revs fluctuate?

What is going on? I asked my old man if it was the clutch going but he says on cars it tends to affect low rev driving and loss of power and acceleration and quite easily noticeable. My bike has only done 3000 miles - it can't be the clutch? There doesn't seem to be a loss of power, i think it still has a 13 horses

Thanks for your help.

Are your revs actually varying or is it just the needle on your rev counter?? - If so it's probably just a minor problem with the instrument and I wouldn't worry about it.

If it is your revs does it only happen on full throttle max power? - If so it's probable just a symptom of the power restriction and I wouldn't worry about it.

Otherwise it sounds like a carb tune is going to be needed or a new spark plug - either way no drama's unless it starts happening at low speed / revs.

Have ya checked that your chain is not to tight (all the way around) ?

Thank-you for your help.

I have checked this chain and it is quite loose even with my brother siting on the bike. I have ridden the bike over 900miles without adjusting the chain.

The bike is not really restricted as such, it is just not tuned unlike the nsr125r.

I think this will solve the porblem. Thanks again.

it could be that your chain is too loose mate, check to see if it has about an inch's worth of free play all the way around, especially if there are any tight spots. Other than that 70mph is the bikes top limit so you could be bouncing off the limit!

It was a loose chain and it is all sorted! Forgot to reply! It was me being lazy riding the bike several hundred miles and only filling it with petrol and occasionaly checking the tyres every so often!

70mph is the "limit on the flat" but there is no restriction, down a steep hill you can get to 80mph so there is nothing mechanical stopping you going 70mph!

Remember to look after your chain mate, if you want I'll show you how I look after mine. Remember it's what connects your engine to your wheels and should be cleaned and lubed regularly and the adjustment checked regularly too.

That's enough about willies, it also applies to your chain too. I clean lubed, well adjusted chain makes all the difference with the bike.

didn't someone on here have an accident beacuse their chain snapped and wrapped round the rear axle and locked the back wheel?

nothing scares me more than having my rear wheel lock on me at highspeed, would take a highside over it if i had the choice.

Ouch! To have it snap that sounds awful, i was told that having a chain too tight is dangerous, too loose is not good but not dangerous.

I may take you up on that offer later funky. I am at uni at the moment so i'll be back in devon in late june.

Too tight and the chain can snap, too loose and it can come off the sprocket...also not good.

Not cleaned and dirt gets into it, not lubed and it won't move properly. Both can cause Tight spots, which are a b1tch to work out, if you can and also degrade the chain, decreasing it's life.

Send me a PM when you fancy. Hope all is going well at uni mate.

Tom L wrote:didn't someone on here have an accident beacuse their chain snapped and wrapped round the rear axle and locked the back wheel?

nothing scares me more than having my rear wheel lock on me at highspeed, would take a highside over it if i had the choice.

The chain snapped on my old CG125, didnt lock the wheel up though.