Author Topic: Manifold Boot / Air Leak Question (Read 10172 times)

jwalters · « **on:** July 04, 2005, 10:28:35 AM »

Hello,
My CB750K2 project bike seems to have a bit of an air leak where the manifold boot meets the manifold. I did the WD-40 test and saw some small bubles between the metal from the manifold and the rubber boot. I have three questions.
1. With the carbs off, and the rubber boots still attached to the engine manifold and fully tightened, should I be able to spin the boots? I ask, because I can spin them and I am wondering if possibly my hose clamps are shot.
2. Here is a picture of my hose clamps When on my bike, these clamps are fully compressed. (ie, the screw cannot be tightened anymore because the faces meet). Is this normal, or has these clamps stretched past their point of usefullness?

3. I noticed this orange stuff around my manifold, which looks like gasket sealer. (Possibly, the previous owner had the same problem I am having, except I am going to fix it correctly). Is this stuff stock, or was this a jerry-rigged solution?

4. And finally, ok, I lied I said only three quesitons. Where can I get some NOS hose clamps online. I would like to stick with stockers, because they fit and look better than Ace Hardware hose clamps.

Thanks a lot!
jesse

eldar · « **Reply #1 on:** July 04, 2005, 02:11:25 PM »

Well you may be able to move the boots a bit but spinning them with little effort means that the clamps are probably stretched.

The orange crud is not standard. It is a gasket sealer made for high temp. Does work for temp fix but thats about it.

now for NOS clamps, I would say you are S O L.

BUT you can check AUTO parts stores and they usually ahve many different kinds of clamps that will like very close to stock PLUS will probably be a better material than NOS and last longer.

jwalters · « **Reply #2 on:** July 04, 2005, 02:19:29 PM »

Hi ho hi ho, off to OReillly's I go!
Thanks for the input!
Jesse

eldar · « **Reply #3 on:** July 04, 2005, 02:41:37 PM »

One thing to check on your boots is for cracks. the rubber should be supple and flexible with no cracks.

cben750f0 · « **Reply #4 on:** July 04, 2005, 03:58:46 PM »

went to my local hydraulics store about a week ago, and got thin stainless clamps that are the exact same width, but do up like normal hose clamp.

my old clamps would do all the way up, and when i pulled thae carbs, the manifolds would come off at the head, which would be ok if i had undone the clamps!!!...

the only thing to look out for is that you dont over tighten the hose clamps and cut your manifolds... peace

can go and take a pic of the clamps if you need..peace

Robert · « **Reply #5 on:** July 04, 2005, 04:15:07 PM »

Not much input from here, just one: take airleaks seriously. It's not a problem to wreck the engine in no time with air leaks that got no attention for too long...

jwalters · « **Reply #6 on:** July 04, 2005, 04:40:07 PM »

Thanks. I have new hose clamps on order from the local honda dealership. The boots seem to be in good shape.
jesse

Raul CB750K1 · « **Reply #7 on:** July 05, 2005, 02:18:18 AM »

A word of advice: the carburetor alloy is not so strong. If you overtighten the clamps you run the risk to break the carb body. They have to be tight but gentle.

Raul

mutters · « **Reply #8 on:** July 05, 2005, 02:50:27 AM »

you might like to use the system we use at work .
tighten it up til it breaks then back off a bit.

cben750f0 · « **Reply #9 on:** July 05, 2005, 03:09:14 AM »

i found that even with new honda clamps that they would do up to the stop, because the rubber had deformed over time... i got the hose clamps so that i could go that little bit more to get a good seal... just a thought new honda clamps may not clamp tight, and you might still have the loose manifolds......i am a maintainance fitter by trade so have a good feel for these things....so i dont think i would break the carbs(

)... though you are right too much tension on anything is a bad idea.... good luck and keep us posted...peace

Mark M · « **Reply #10 on:** July 05, 2005, 03:40:10 AM »

I spoke to David Siler's about these clamps about a year ago - they do have 'some' clamps but they are painted black and are very expensive, over £5.00 each I seem to remember.

I very much doubt the problem is your clamps stretching, much more likely that the rubbers are deformed, as these work out much cheeper than the clamps I know which I would look to replace.

BTW they are designed to be done up to the point where the clamp faces meet, just. Another soultion would be to fit a spacer under the clamp band, an rubber band wraped round the rubber may do the trick.

Bob Wessner · « **Reply #11 on:** July 05, 2005, 04:20:12 AM »

I've been following this post and though have not encountered the problem as yet, I agree with Mark. First thing I would try is to take of up the slack if you will, caused by years of pressure on the rubber manifolds themselves. Anything thin that would handle the environment and not deteriorate should work. I was even thinking that perhaps some thin aluminum cut in strips not unlike the dimensions of the bands might work. Wrap them in the grooves in the rubber then try putting the clamps back on and see if that doesn't snug things up again.

jwalters · « **Reply #12 on:** July 05, 2005, 08:03:43 AM »

Thanks for all the replies. I stopped at the local honda dealer and Mark you were right. The clamps are $9 each!

As far as the rubber boots, mine appear to be in really good shape. I think I might take Bob's advice and fit some sort of rubber spacer in the manifold groove. I am thinking this would seal better than an aluminum strip, but have the same effect. I'll keep you posted.

Bob Wessner · « **Reply #13 on:** July 05, 2005, 08:26:18 AM »

Whatever you try as a spacer, don't make it too thick. You would be surprised how much 'slack' will be taken up going around the entire circumferance of the rubber.

eldar · « **Reply #14 on:** July 05, 2005, 01:42:38 PM »

Well I have never seen these hoses get deformed but ok. I would still go to an outo parts store and get new clamps. Using a spacer is just a temporary cure and you will need to get new clamps or rubbers anyways. If you look around a bit, you will find many different styles of hose clamps. Besides it is not like the honda clamps are beauty pagents winners!

cben750f0 · « **Reply #15 on:** July 05, 2005, 04:41:54 PM »

i'll go out and take apic of the clamps i used...$3.50AUD thats about a third of replacement ones in OZ.. elder have you ever taken a hose clamp off a radiator hose on a car, or the like... you get a deformation were the clamp was, so if you clamp has a stop on it , over time you would be un able to keep a seel, especially if you are taking that hose on and off a bit(like removeing carbs).. this is the reason i sujusted thin line hose clamps...NEway am going to take picture of mine... peace

jwalters · « **Reply #16 on:** July 05, 2005, 04:56:57 PM »

I ordered 4 new honda NOS clamps @ $36 for the set.

The clamps on the carb side are still fine, so I am going to replace the manifold side for now (that was the only side leaking too). As mentioned, the hoses are in great shape and are not deformed a bit. So, I'll give this a try and post the results. I should have the new clamps in a day or two.
Thanks again, all of you!

cben750f1, I am anxiously awaiting those pics!
jesse

x2qwk4ux · « **Reply #17 on:** July 05, 2005, 05:12:14 PM »

Mark's the most correct one here...the rubber dries / shrinks with age. Ever try to stretch a piece of stainless? I suppose it's possible, but aside from the bolt-hole areas that many a gorilla has probably over-torqued, I'd say your clamps are fine.

I'd suggest you purchase new intake rubbers from davidsilverspares, and in the meantime...use aftermarket hose clamps that are no wider than the stock ones. Once your new rubbers arrive, use your old clamps. The old clamps are less likely to loosen compared to the worm-screw type hose-clamps.

Good luck,

Josh

cben750f0 · « **Reply #18 on:** July 05, 2005, 05:20:57 PM »

here we go...

eldar · « **Reply #19 on:** July 05, 2005, 07:30:10 PM »

OK now I see what you mean by deformation. Use a clamp that completely encircles. and then this deformation is kept to a minimum since there is no "open" point.

bearcatamo · « **Reply #20 on:** July 06, 2005, 08:59:13 AM »

As far as the clamps are concerned, check with oldbikebarn.com. they may have them as they tried to sell me set last week when I ordered my new manifolds.

Barry

jwalters · « **Reply #21 on:** July 06, 2005, 01:01:59 PM »

Seems that installing the new NOS clamps and cleaning up all the old gasket sealer around the manifold cleaned up my air leak problem. Unfortunately, my bike still runs like crap when I crack open the throttle. I've checked all the common things, float height, needle position, timing, etc. All seem to be ok, I've experimented with stock main jets of 105, tried 110, 120's and even 130s.

It still seems to make a (pardon my french) farting noise when I really open the throttle. The bike feels like it's not firing, or speratically firing at best when I whip the throttle open. I've check my coils, and plugs and they seem to be firing well at all rpm ranges. It only lets me get up to about 35 or 40 mph b/c of this too before it boggs down. I am running stock exhaust, with pods intake filters and I've gone through the faq over and over again but to no avail.

The only other thing I can think of is a fuel delivery problem. I am going to install some temperary clear gas tubing to make my fuel system a little more visable.

TwoTired · « **Reply #22 on:** July 06, 2005, 01:33:42 PM »

Perhaps it's time to take a step back?
Have you done all the major tune up items?
Did the compression test show even cylinders?
Does partial choke application help?
Have you turned your air bleed screws IN?

Fuel starvation ought to make the spark plugs read white?

What are your plug part numbers?

Is your timing advance working?

Is the rude noise coming from the exhaust or intake?

Bob Wessner · « **Reply #23 on:** July 06, 2005, 01:46:37 PM »

To add to the list above, how about float height?

jwalters · « **Reply #24 on:** July 06, 2005, 01:58:00 PM »

As mentioned in my previous post Bob, float height is correct.

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Author Topic: Manifold Boot / Air Leak Question (Read 10172 times)

eldar

eldar

eldar

x2qwk4ux

eldar

bearcatamo