Changing The Camshafts On My Bike.

[Aleks]

Hi guys and gals, I have a question for the people with a bit more experience with bikes than me...

I have a Honda Varadero XL125 53 plate and it will go to 70 quite happily, the problem is ill be at about 11,500 rpm which means my bike will be revving its tits off and drinking fuel. All the power is also from 10-11k rpm which is not great for commuting as it struggles to go at traffic lights, and therefore the power is obviously better mid range in this case.

So I was wondering, could I get a camshaft which would give me better mid range power and put a smaller sprocket on the back and get away with it? Keeping in mind I still want the bike to cruise at 70 easily and at a lower rpm? I know I could just put a smaller sprocket on the back but then I dont think it would cruise at 70 so easily, and it would stuggle setting off.

Sorry about the paragraphs... I really appreciate your time

P.S. I know its just a 125, but I bought it to have as a project/experiment because I want to learn to modify bikes and cars in the future.

Cheers!

 

[Captain]

Always understood that changing the sprocket size will alter the acceleration on a bike.

The camshaft will change the stroke profile which has an effect on the acceleration and also top speed. But I very much doubt you'll get the best of both worlds.

I use a Yamaha R125 as a commuter bike and although acceleration is adequate for the commute. The top speed is around 80mph close to the limiter. However it takes an age to reach top speed and you'll maybe find that by lowering the rev range at 70 for cruising it could drop the engine out of the power band meaning that with even a slight gradient the bike will slow.

The other option wouldbe to fit a 150cc or 180cc cylinder kit to the engine but in the case of the Yamaha this can dramatically shorten the clutch and gearbox lifespan.

 

[Aleks]

Always understood that changing the sprocket size will alter the acceleration on a bike.

The camshaft will change the stroke profile which has an effect on the acceleration and also top speed. But I very much doubt you'll get the best of both worlds.

I use a Yamaha R125 as a commuter bike and although acceleration is adequate for the commute. The top speed is around 80mph close to the limiter. However it takes an age to reach top speed and you'll maybe find that by lowering the rev range at 70 for cruising it could drop the engine out of the power band meaning that with even a slight gradient the bike will slow.

The other option wouldbe to fit a 150cc or 180cc cylinder kit to the engine but in the case of the Yamaha this can dramatically shorten the clutch and gearbox lifespan.

I've had a bit of a play on a Yamaha R125 and an MT-125 and both of the bikes are fortunate enough to have a 6th gear, whereas the baby varadero only has 5. Also, the cheapest big bore kit which would fit her (that I could find) costs just short of £500 and I would need to send the barrels away for 2 weeks. The same company also does camshafts but they also focus on top end power.

Thanks for your suggestions though

 

[Lurch]

It is horses for courses really. A 125 isn't really designed for high speed or rapid acceleration.

Also a Varadero certainly won't have been designed to be quick. It's designed to do what it does solidly and reliably. If you want speed and acceleration then you need a sports bike or a bigger bike.

I'm aware it might be a limit on the licence front, but you need to play your cards how they're dealt and not put yourself in a position the bike can't get you out of.

Getting involved in redesigning an engine is seriously specialist stuff. The only place to find help in getting more from your bike on that front is going to be a forum that specialises in your bike.

 

[Aleks]

It is horses for courses really. A 125 isn't really designed for high speed or rapid acceleration.

Also a Varadero certainly won't have been designed to be quick. It's designed to do what it does solidly and reliably. If you want speed and acceleration then you need a sports bike or a bigger bike.

I'm aware it might be a limit on the licence front, but you need to play your cards how they're dealt and not put yourself in a position the bike can't get you out of.

Getting involved in redesigning an engine is seriously specialist stuff. The only place to find help in getting more from your bike on that front is going to be a forum that specialises in your bike.

Thanks for you reply BTW I forgot to mention that im not bothered about going any faster, I just want to be able to cruise on the bike with better mpg.

 

[Captain]

I would suggest changing the sprockets then.

 

[Lurch]

I would suggest changing the sprockets then.

Probably easier, bearing in mind it'll affect your speedo. If you have a electronic speedo rather than cable then you can sometimes you can recalibrate it, but may be a dealer job.

What gives with one hand though takes away with the other.

 

[Captain]

Speedo reading is usually taken from the front wheel. Do you have a cable going into the front wheel hub?

 

[Aleks]

I would suggest changing the sprockets then.

I could do that but that means i would get worse acceleration as well.

 

[Aleks]

Speedo reading is usually taken from the front wheel. Do you have a cable going into the front wheel hub?

Yeah the speedo reads off the front wheel so changing the sprockets wouldnt be a problem thankfully.

 

[Captain]

Yeah the speedo reads off the front wheel so changing the sprockets wouldnt be a problem thankfully.

At least it will be cheaper than messing about changing the camshaft. And quicker. And less messy.