[Jon Bruce]

I have a 2000 748 that is running great except ...

When riding at a constant speed, the bike starts "surging" almost like I'm giving the throttle a quick twist and then letting it go. This does not seem to happen when I'm accelerating; acceleration seems quite smooth.

I can feel the same (or at least similar) when I'm in gear and coasting to a stop (but still with enough rpms to not stall the bike). I do not feel this at all in neutral or when I pull the clutch. It *seems* to be tied to the engine/drive.

I first noticed it very slightly a couple of years ago, towards the end of last year it got a bit worse, and this year I'm growing rather concerned (and annoyed).

I have checked the chain against the manual and it seems to be the correct tightness/looseness. I don't see any physical wear on the sprockets.

Any help would be appreciated, thank you.

 

[tye1138]

It very well could be a fueling issue, thats kinda how they start. Since its an old bike, perhaps starting with the fuel filter AND cleaning the injectors first, may be a good idea. It needs to be done no matter what and it will give you a good sense of the problem after thats done. If the problem persists, I'd then look at the throttle position sensor, as they can go bad over time.

 

[Jon Bruce]

That sounds like a good idea, I'll order a new filter and such.

I did the filter a couple of years ago, but it's not a bad idea to do it again.

I'm not sure that is the main problem though, I can leave the bike in neutral and it revs fine, holds an RPM file (any RPM). The problem only seems to happen when in gear with load on the wheels.

Again, I'll hit up that filter, it never hurts.

 

[tye1138]

Yea, if its under load, its most likely fueling.

 

[Jon Bruce]

Something didn't seem right as I was typing my first message, so I took my camera and put the bike on its rear stand. Here is about a minute of the chain and sprockets.

I think it's time for a new chain and rear sprocket. I'm not sure if some of that is because there is no load on the rear wheel, or even if that could cause my problem, but the chain and sprocket are toast (I've cleaned and oiled the chain very recently and it feels like a solid piece).

I'll still do the fuel filter, I'm sure it needs done as well. Could the chain and sprocket be causing what I'm seeing or should I keep digging?

 

[tye1138]

Umm.. yea, didn't you say there wasn't any wear on the sprockets? LOL

I think you've found the problem!

Don't touch anything else until you replace the chain and BOTH sprockets.

 

[Jon Bruce]

I totally did! After I typed it, I though I'd better go have a really good look. It was hard to see in the dim light, but a little flash light took care of that.

 

[motowheels]

Get one of these steel /aluminum sprockets:


SUPERSPROX Stealth 520 Sprocket: 748-998
Lasts a long time. Less expensive and lighter than OEM. It also has backing plates to prevent worn/damaged cush drives from backing out into the swingarm.


DRIVEN Light Front Sprocket 520/14T
light weight drilled out version


D.I.D 520 ERV3 Chain
Great chain

 

[garylkendall]

did you buy a horse of a ducati????????????? didnt know they used ducatis in the rodeo!!!!!!! lol

ya its time for a new chain and sprockets, about 5000 miles ago that is.

 

[NOVADUC]

Oh I see chain correct