Repairing intake manifolds with bike tubes

Hi!

I saw someone's post about a way to fix leaks in manifolds. I also have leaky manifolds! I can't really afford a whole new set at the moment, so I'm going to try to get by with this trick.

Right now the manifolds are sitting and drying. I'll post in this thread with results to let you know how they work.

Click here to see a gallery of how I went about it

A quick picture of the completed units:

 

Once the RTV dries I'll go and trim down the excess stuff at the ends which should make them look fairly clean!

 

Looks like a tidy mod to get more usefull life out off those againg boots.

Other option include Heatshrink Tubing
http://www.nelcoproducts.com/shopping/s ... ink+Tubing

And Heatshrink Fabric
http://www.buyheatshrink.com/heatshrink ... bric.htm#B

Ghost

 

Hmm.. cleaned them up and put them back on the bike and it seemed to actually be running a lot better that it ever has.. for a couple minutes. Once it got up to temp it went back to running way lean, backfiring, and hanging revs.

Could that just be because the engine was maybe getting too hot? it is really hot outside and I was just running in the garage (lightly air conditioned, with ventillation) and it was overheating? I mean.. I don't even know anymore!

 

Hi Tresch. I'm curious about your situation. What did you do to determine that the manifolds were leaky before the repair? (carb cleaner spray test or propane gas test) Were your boots cracked all the way through? Have you determined if your repair is failing somewhere specifically or assuming because the symptom has remained the same? It seems like it should have worked if that was the problem in the first place. Good luck and post here again if you dig deeper and find out something.

 

I'd suggest that you are looking at dried out throttle-shaft seals. With all the RTV and inner tube repair, you're probably not sucking air there anymore. Next places to look would be throttle shaft seals or the airbox to carb boots, which also need to be on nice and tight so you don't suck extra air. So, try those two things................

Dave

 

Vacuum leak was confirmed by spraying ether at them.

I already replaced the throttle shaft seals last week, it seemingly had no effect on the running of the bike.

airbox-to-carb boots are on there reasonably well but wouldn't cause quite this drastic of a problem, I wouldn't think.

Plus, I just re-checked with the ether. cylinder 4 was still leaking cause I didn't have the clamp tight enough, and that helped a little, but cylinder 2 (or 3, hard to tell which is actually sucking) still causes revving when sprayed with ether. So either it's the manifolds, or the throttle shaft seals I just bought new from xj4ever are not actually sealing so well. I'm inclined to think it's the manifolds.

possibility that maybe I was a little too eager and put them back on the bike before the RTV cured in all the right places, and the vacuum from the running engine found its way through.

or that maybe with all that extra rubber on there the clamps are clamping firm enough on the ends to get them to cynch down tight enough on the carbs themselves.

 

also for reference I also have brand new manifold-to-head gaskets.

Basically everything is new except the manifolds!

 

Tresh what is your problem to begin with apparently your trying to get your bike t run right but what are your symptoms?

 

That's one of the first things I had to address when I got my 750 Seca. The carbs were in need of service, so as long as I had them off, I decided to fix the intake boots at the same time. I used GOOP to seal all the cracks and it worked perfect. Just a thin layer over the outside of the boots and it's good to go. That was about 8 years ago and they are still in good shape. The GOOP is clear, so you can't even tell they have been coated with that stuff. It sets up like tire rubber so it stayed plyable too. Try it!

 

problems:

*)light backfiring (less after it's warming up)

*)hanging revs. Won't fall down to idle

*)impossible idle. Will tend to slooowly die out until you constantly tend to the gas. If you adjust the idle higher, then it never actually gets down to idle and will just rev up to 3k RPM and hold there. the "magic point" where it mostly idles is tiny and moves as the engine warms up over a period of about 15-20 minutes. During this time you have to always have to tend the throttle, or be constantly adjusting the idle screw.

 

I snugged down the manifolds more and wasn't actually able to really find anything conclusive with the starter fluid, so i think if I have leaks, they're minimal.

At this point I'm wondering if it's just set lean, like a previous owner fiddled with the mixtures and they're all out of whack! Where the heck ARE the mixture screws on these, anyway?

I've had the carbs completely apart and totally cleaned, floats checked, carbs bench synced, valves adjusted.

I just took it for a ride and frankly it runs great, just has all these lean symptoms. I'm SO CLOSE!

 

Okay, now I feel like a huge dufus.

I had those carbs completely disassembled. Every piece... except somehow I never spotted the pilot mixture screws.

I've been operating under the assumption that those are set from the factory and if I get everything else set to spec then I should at least be CLOSE.

Welp... I found 'em. Turns out a previous owner had indeed drilled out the brass plugs and messed with the tuning. Bwahahahaha.

I don't feel bad because I know I DID have some vacuum leaks in there, so I feel a bit more secure now about tuning the mixture. I just went and bottomed them all out (they were at 3 turns, 2.5 turns, almost 4 turns, and about 3 turns, respectively) and set them all to 3.

It's still a tad lean but frankly it's running better now than it ever has in the 5 years I've ridden it. Time now for fine-tweaking!

 

oh yeah and it's IDLING. IT IDLES! BY ITSELF!!!!!

 

Has anybody tried using silicone rescue tape to repair the manifold boots? I just finished the bike tube repair myself (still need to re-mount the manifolds). After finishing the bike tube repair I saw that stuff at the dive shop, and it looks like a great solution to repair the leaks.

http://www.amazon.com/Rescue-Tape-Self- ... B000ZTK6CI