Odd Sized Countershaft Spline

[hotshoerob]

I went to change my chain and sprockets last weekend and found the Sunstar front sprocket would not fit the spline.

When I took a good look at it the spline size is different. The shaft is the same diameter and the number of teeth is right, it's the size of the teeth that's the problem.

I contacted Sunstar, sent them pictures and they say they are puzzled. All years of VFR800's use the same sprocket / part numbers.

Right now there is a stock Honda rubber damped sprocket installed.

So has anybody else ever come across this one?

Here are some pics.

[FJ12Ryder]

That sprocket looks totally FUBAR'ed. How about another picture of the splines looking at them from the top/side.

[JZH]

That does not look good. How many miles on the engine?

Can't tell from the shaft, but the sprocket should look like the new one...

Ciao,

[hotshoerob]

No, the spline is a different size. The new sprocket will not go on, no way.

Look at the width of the teeth on the countershaft, the external part of the spline teeth are wider than the internal part.

On the replacement sprocket they are about equal.

There is a little wear on the countershaft and a bit of play with the original sprocket installed, but not bad, I've seen worse.

[vfrcapn]

Is this a Japanese import? It looks like the '98-'01 non-North American bikes had a different sprocket? Maybe someone can look it up to be sure..

According to the Suntour sprocket guide it looks like the Japanese bikes '98-'01 use the same sprocket as the big VF's, DOHC 750 and others. Different than all the other 5-6G bikes.

[aokman]

I've got a 1999 Australian model (Japanese import) and I just got a new sprocket kit from the US and it went straight on, had to play for a little while to get on as it was snug but yeah :)

My old sprocket had some wear on the splines aswell and had started to move off to the left.

Comparing the 2 pictures, it looks like the new sprocket is the correct one? I count 13 splines and there would be more or less if it was a different overall size. I would measure the ID of both and the distance edge to edge of the valleys if they are the same then it has to fit, mine didn't look like it would fit till it slipped on.

[aokman]

here is mine...

[FJ12Ryder]

Slather some anti seize on the shaft when you put that sprocket back on, that will help keep wear to a minimum.

[hotshoerob]

Thanks for your comments and pic aokman. Yours sure looks the same as mine. Maybe I just didn't try hard enough. And with the old one being worn it slips on easy, of course.

I'll give it another go tomorrow.

[RDMcD]

I installed a set of sunstar sprockets last year, went on with no problems. I can check the part # if you want.

From your pictures it looks like the splines are wore quite a bit, normally splines don't wear unless the sprockets gets loose. Was the bolt tight when you removed it? If the old sprocket has been hammering on the shafts every time you accelerate and downshift it may have enlarged the tips of the splines enough that the new sprocket won't slide over. Take some measurements, you may just have to touch up the shafts with a file.Once the new sprocket goes on maybe you can use some shim stock pieces to tighten up the splines?

[hotshoerob]

Okay, everything is good. With a little wiggling and jiggling it slipped on.

When I first tried, it didn't look right, not like me to give up that easy.

Yeah, that old one was totally shot. I'm surprised the spline was actually worn more than the chain teeth.

The bolt was tight when I removed it. I'm not sure how old it was but I've put 25k miles on the bike myself.

Thanks again to aokman.

[FJ12Ryder]

I would keep a very close eye on the shaft. If the sprocket was worn that badly the shaft can't be in the best of shape. A worn shaft will ruin a new sprocket in pretty short order, especially in stop-and-go traffic. Maybe put a thousand miles on it and pull the sprocket off and see if you're getting any wear. Tightening the nut is not going to keep the sprocket from moving around if the shaft is worn badly. The last thing you want is for that sprocket/shaft to go south completely while you're out on the road. Did you put some anti-seize on the shaft before installing the sprocket? Anything that keeps metal to metal contact to a minimum is a good thing.

You may be looking at replacing the countershaft sprocket shaft at a future date. Bummer, but possible.

[JZH]

It would cheaper to replace the engine, really.

Also, doesn't the countershaft sprocket move laterally by design? The nut is not supposed to do anything other than keep it from coming off the end of the shaft.

ISTR someone on this side of the pond with a similar issue, where the shaft was worn so much that it allowed noticeable forward and backward movement of the sprocket as well. I think the "solution" was to fit a new sprocket and JB Weld it in place, reasoning that he'd at least get a sprocket's worth of miles out of the old engine before scrapping it (or the bike)...

Ciao,

[aokman]

I would keep a very close eye on the shaft. If the sprocket was worn that badly the shaft can't be in the best of shape. A worn shaft will ruin a new sprocket in pretty short order, especially in stop-and-go traffic. Maybe put a thousand miles on it and pull the sprocket off and see if you're getting any wear. Tightening the nut is not going to keep the sprocket from moving around if the shaft is worn badly. The last thing you want is for that sprocket/shaft to go south completely while you're out on the road. Did you put some anti-seize on the shaft before installing the sprocket? Anything that keeps metal to metal contact to a minimum is a good thing.

You may be looking at replacing the countershaft sprocket shaft at a future date. Bummer, but possible.

In most applications like this, I would expect the output spline to be made of a hardened material and the sprocket is usually made of a softer material on purpose so it becomes a sacrificial part. It should be pritty obvious if there is backlash in the sprocket with it just sitting on there :)

I would expect most wear to come from non-Honda sprockets as they are likely to be made from harder materials to try and extend life while Honda probably engineer their sprockets differently.

If there is any backlash in the sprocket then the wear is likely to continue and accelerate as the movement increases. My old one had moved a bit sideways but the output shaft is still very snug.

[FJ12Ryder]

The output shaft may be surface hardened, which means it's going to wear more quickly once you break through the top layer, but if the surface is still good you should be fine. But any kind of rotational slack is not good at all.