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[PeteF]

Can anyone tell me the size of the engine sprocket on the Euro 4 Classic? I understand it's different from the pre-Euro 4 machines.
I find the bike rather under geared and want to alter it as soon as it's run-in but I can't think of a way of counting the teeth without removing the engine casing.
Has anyone altered this?

[sofiaspin]

I posted this a couple of months ago. An 18th sprocket has made a difference but a 19th would not go amiss. I doubt I will bother, however, as spent enough sorting out the bike into something that goes better, vibrates less and has decent turn of speed.

viewtopic.php?f=3&t=9446

[Chris H.]

I believe that the Euro4 has 18 tooth front sprocket that can be changed to a 19 tooth. Unless you tune the bike up you will lose top speed as it will be impossible to reach full power. You will also have to rev the bike harder in 4th gear and will find you will have to change down more often on hills. I would recommend emailing of asking our Hosts advice.

I think the following may also be true:
"On 500cc EFI bikes the chain size for 17T sprocket is 101 links; that for the 18T (and 19T) sprockets is 102 links"

[Haggis]

Euro 3 is 18, Euro 4 comes with a 17 on the C5. I run a 19 on my Euro 3 but I have other tuning mods to be able to pull that gear.

[sofiaspin]

Just to clarify - Euro 4 C5 has a 17th front sprocket. My euro 3 Conti GT has an 18th front sprocket. It seems the Euro 4 models dropped a tooth. So reverting to an 18 tooth front sprocket simply takes them back to where they have been for some time. It is not the case that you cant rev the Euro 4 C5 bike to full power with an 18 tooth sprocket. It has not lost any acceleration or top end - it is just that the journey getting there is a bit smoother and just as rapid - for a Bullet. The only mods on my Euro 4 C5 are Hitchcocks 50s style silencer and a K&N filter - that was enough to cause mayhem with the fuel injection and air injection system and sensors. So the bike now has a power commander. The exhaust and air filter changes perhaps added a modest 2 bhp at the rear wheel - which is now 23bhp. The torque curve is flat - which is why I like Bullets!

[Haggis]

Mines is similar, euro3 with a k&n plus large bore header with an absorption type can, a little bit of head work and porting and better valves plus PCV set up on a Dyno. It can plod along at 65 all day long with a very leisurely heartbeat. I doubt it will rev out in top with the 19 fitted but that's not why I fitted it.

[PeteF]

Thanks guys.
I don't want to achieve top speed but do want a more leisurely ride at 60/65.
I think 19 tooth is the way to go from what you say.
I have the option of replacing the rear sprocket of course without removing the R/H engine cover.
I'll ponder that.

[sofiaspin]

I think you mean upping the front sprocket from 17 teeth - which is how it comes - to 18 teeth. It was suggested I needed a 102 pitch chain but the standard chain worked fine - it had stretched a bit. A 19 tooth sprocket will need the longer chain.

[stinkwheel]

Just a point of order. The engine sprocket is the one attached to the drive shaft of the crank and is part of the primary drive. The "front" sprocket is also known as the gearbox sprocket. It is attached to the gearbox output shaft and is part of the final drive.

Overall gearing can be altered by adjusting the size of either but it is more usual to change the gearbox sprocket than the engine sprocket because you would usually need to change the primary drive chain at the same time.

[PeteF]

Well no, Sofiaspin, I mean 19 teeth.
The Classic used to come with 18 and people upped it to 19 (or even 20)
I can't imagine why it now comes with 17 teeth but I don't see why I can't go to 19.
I does seem very under geared to me.
I'm not doing this til it's run-in of course.

Yes Stinkwheel, I know