Very High Idle

[fatbiker]

I think I may have found the problem. Got the bike running at a lower RPM; 4K to be exact and sprayed some carb cleaner on every spot I though could possibly cause an air leak. Tried ether first with no effect. I found three spots below the carbs and near the intake manifold that when sprayed resulted in the engine bogging down. I assume that since the spots are past the carbs that it's raw fuel mixing with air causing the engine to receive too rich a mixture therefore resulting in an uneven burn. Was that technical enough?

I have attached an expert picture pointing out the exact spots where I sprayed the carb cleaner. Good thing I'm in sales and not design.

I assume that the problem is a result of one of three things; leaky intake manifold gaskets; leaky carb boots; or possibly leaky v-boost boots. They all look like they are original parts so I'm going to order everything and replace them. If anyone thinks it might be something else I am all ears.

Fatbiker

 

[fatbiker]

Looking at this picture I can see that the manifold uses O-rings as opposed to a gasket. Anyone ever have the O-rings go bad? Also, the bolts holding the manifold are stuck good. Any advice for removing them?

 

[jfeagins]

Is the A/F mix screw hole partially broken out on that left carb in the picture?

How did you get the bike to run 2K lower rpms?

With the carbs off, you should be able to see weather cracking in all those rubber boot parts easy enough, if it isn't already apparent enough with them mounted. In some cases, that cracking can be only superficial and not all the way through to where they would case any problems.

You can Email Sean Morley of this forum for any/all parts you may need, and I believe he stocks most of them at all times. [email protected]. Dannymax probably has them as well.

 

[jfeagins]

Looking at this picture I can see that the manifold uses O-rings as opposed to a gasket. Anyone ever have the O-rings go bad? Also, the bolts holding the manifold are stuck good. Any advice for removing them?

Mine are 29 yrs old and never been off. Still breathing properly. But I have had to replace all the airbox boots (just recently) and also the ones under the carbs (a few yrs ago). Also been through a couple sets of diaphrams over the years & a couple coasting enrichener valve diaphrams (my unwise use of spray carb cleaner).

 

[fatbiker]

Yes, some of the hole going to the a/f screw is broken and missing. I sprayed carb cleaner in that area and found no change in idle.

I was able to bring the rpm's down by adjusting the two right carbs way out of sync. When in sync with the other carbs the rpm goes to 6k and climbs. I am going to order new carb boots first and see if they help. If not then vboost boots. Does the intake manifold need to be remove to change the vboost boots? Also, is $75 a good price for a set of 4 new carb boots?

 

[jfeagins]

Does the intake manifold need to be remove to change the vboost boots? I believe they do. Also, is $75 a good price for a set of 4 new carb boots? Sounds about right.

$69.99 including shipping at Partzilla.com

Morley may have a better price.

 

[veebooster]

I found my vboost boots cracked under the clamps. You couldn`t see it until completely taken off. I believe they were like that from the factory as the clamps were way over tightened and the bike was only 2 years old at that time.

Dale

 

[fatbiker]

Ordered the carb boots from Partzilla. Thanks Jfeagins!

Veebooster, when you replaced your vboost boots did you have to remove the intake manifold to do so?

Fatbiker

 

[m-cman]

If you had the carbs completely apart, are you sure you reassembled properly? Especially the areas with the little springs that are near the sync and idle adjustment screws. Those being assembled incorrectly along with the idle adjustment screws could cause these problems.

 

[fatbiker]

Yes m-cman, I'm pretty sure they are assembled correctly. The carbs are off right now so I'll take a look and make sure first thing tomorrow. The carb cleaner test proved there is vacuum leak somewhere near the bottom of the carbs so I'm going to stick with the program and replace carb boots first, vboost boots second, then go from there.

Fatbiker

 

[jfeagins]

If you had the carbs completely apart, are you sure you reassembled properly? Especially the areas with the little springs that are near the sync and idle adjustment screws. Those being assembled incorrectly along with the idle adjustment screws could cause these problems.

I thought the same thing, but discounted it, as he stated early on that all the butterfies were closely matched and/or closed. I'd think an incorrectly assembled linkage would show up when observing the butterfies from above. One or more would be visibly propped slightly open, wouldn't they?

 

[dannymax]

Looking at this picture I can see that the manifold uses O-rings as opposed to a gasket. Anyone ever have the O-rings go bad? Also, the bolts holding the manifold are stuck good. Any advice for removing them?

I had one o-ring on my '99 fail, it was installed incorrectly at the factory and lasted for 6 or 8 years before finally giving up.

If you do remove the manifolds (and if they haven't previously been removed) there are two of the eight allen bolts that are different from the rest....the left front and right rear bolts, (or the forward bolt on the #2 carb and rear bolt on the #3 carb). They are slightly shorter, should have a small blob of silicone on the ends and will probly be a stainless color instead of black.

Replace these bolts in the holes they were removed from.

Try an impact wrench on the bolts.

 

[veebooster]

Ordered the carb boots from Partzilla. Thanks Jfeagins!

Veebooster, when you replaced your vboost boots did you have to remove the intake manifold to do so?

Fatbiker

It been a long time but as I recall yes. Inspect those Orings and as mentioned be careful about the bolts. U need some yamabond for the one. A clymer manual explains it quite nicely. Good luck, you'll find it!

Dale

 

[sdt354]

It been a long time but as I recall yes. Inspect those Orings and as mentioned be careful about the bolts. U need some yamabond for the one. A clymer manual explains it quite nicely. Good luck, you'll find it!

Dale

I've always used high- temp silicon around the manifold o-rings,even new. It just made sense to me. But,I'm anal about intake leaks.

 

[fatbiker]

As I mentioned earlier I ordered new slides with diaphragms from a local bike shop. After two weeks waiting he notified me that his vendor is not longer able to get either the slides with diaphragms or even diaphragms by themselves anymore. They say the supplier they get them from has discontinued them permanently. So, I had to make a decision; buy slides/diaphragms from someone else and hope that fixed the problem or buy a good, working set of carbs from CaptainKyle. I figured if the new diaphragms didn't work I'd have to send my carbs out to someone and spend another $150 plus shipping to get them cleaned. That doesn't included any needed parts. CaptainKyle gave me a good deal on the carbs so I bought them. Put them on today and the bike idles and runs perfect!

So, the big question is; what is wrong with the old carbs and why do they idle at 6K?? Well, I ordered new carb boots and they didn't fix the problem. I took my slides/diaphragms to my local bike shop and he held them up to a bright light and showed me all the holes and thin spots. Lots of them! Especialy the two on the right hand side carbs that I couldn't sync. Considering that these are vacuum actuated carbs the diaphragms were more than likely the problem. Next guess are the other diaphragms located inside the carbs. Can't remember what they are called but they looked like they were 28 years old as well.

The story ends with the bike running great thanks to CaptainKyle's used carbs and I had a great time testing the v-boost today!

A HUGE thanks to everyone who lent their advice!! This forum has been an invaluable resource to me since I picked up my project bike and I hope that someday I can share what I've learned with someone in need. You guys rock!

Fatbiker

 

[CaptainKyle]

Glad your happy with them I figured you would be since it had not been that long since I went thru them & they were running great on my girl friends bike. Oh well I am happy now to since I switched them out and have the stage 7 on my girl friends bike so it runs a little better when I wanna play on it.:biglaugh:

 

[Mr. Max]

Was the throttle cable right way (push/pull), did throttle feel normal? Might be one reason for high idle, maybe..