manifold boots

Is it common that old, hard manifold boots will give you problems getting your bike to run correctly? I have been told that this is the case and that no amount of sealant will fix it. On this testimony I bought new ones (haven't gotten to use them yet). Anyone else ran into this?

Thanks

Just let your bike idle, if it will, and spray a little carb cleaner, or WD40 around the manifold where they meet the head. The engine will race or bog each time you spray, if you have bad seals. BYW, the rubber caps on the sychronizer nipples may also be bad.

Post edited by: TLH101, at: 2006/02/10 14:17

That's exactly what I experienced with my Ride. They appeared ok on the outside but since some of my other seals were bad (tach seal, fork seals etc.) I went ahead and got the replacement intake boots as well. It was like night and day. And when I got the old ones off it was obvious that they were bad.
The carb cleaner/WD40 trick I learned from my brother who has operated auto shops and will tell you real quick if it is leaking or not.

funnily enough I have just managed to track down a set of original new carb to airbox rubber hoses and springs to replace the rock hard ones on the 650 this weekend.

I spend a lot of time mounting carbs and when I test KZ650 (VM24) carbs I use the intake manifolds from a VM26/28. I use regular hose clamps and crank them down good and generally get a good seal. You can tell right away when you try and sync the carbs if one is leaking between venturi and intake manifolds. When this happens, I just shove the rack UP a bit or DOWN a bit and will see the leak magically disappear. It is then time to reseat them and reclamp them...

Why bring this up? I have tried WD40 trick to see if it would pick up the leak and it seldom works for me. I have seen a LOT of intake manifolds as many customers will leave their old ones attached to the carbs and most folks have old and hard intake manifolds that have no cracks but would not seat well due to the brittle nature of the rubber. I know they are kind of pricey but I would recommend changing those things every few years, if possible; especially if you have to remove your carbs every once in awhile.

The effect of bad intake manifold seal or worse, cracks? First, you can't sync the carbs and the bike will run rough at a minimum. Second, the bike may not idle well... the air leak will cause the idle to race and the bike to not idle down when you let off the throttle. Last, (but not least), the air can focus on the piston crown and hole a piston. I know as I have been there and done that.

Fixing cracks? If they are cracked, they won't seal anyway so it is a waste to try it. If you cover the cracks with silicon, the intake manifolds are very likely too hard to seal. On a bike I picked up a few years ago, I attempted to fix some cracked intake manifolds... the bike ran nicely... well for about 40 miles and then some air was sucked into the #2 combustion chamber; more than likely a bad seal rather than the cracks and I holed a piston. An expensive bit of education! Keep in mind that most aftermarket rubber bits for a KZ are pretty much junk and harden and crack in just a couple years... The intake manifolds fall into the category of aftermarket rubber bit...

One of the best cures for hard rubber is to coat the parts generously with aerosol silicone such as "camp dry" and vacuum seal them for about a week. I have a set for a 650 that were rock hard and they are like new after being sprayed and sealed. The unfortunate part is it won't do anything for cracks.

WG - in the case of the intake manifolds for the Z1 and KZ650, the aftermarket and OEM parts are the same parts - just a different price. They are made by the same company and have the identical mold marks - in fact the aftermarket ones are usually better as they have been manufactured this century, whereas many of the OEM versions have been sitting around for 20-25 years.