| Author |
Message |
    
Ricardoblack
| | Posted on Wednesday, May 28, 2008 - 07:36 am: | 
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I appologise in advance as I know a lot has been writen on this subject already.I think I have read most of it but I can't cure the problem.
I have the typical symtoms of Intake leek popping and banging on overrun surging etc.
On spraying the manifold with carb cleaner revs go up.
I have now changed the Intake seals 3 times.First time non Harley seals fitted dry they leeked.Second time fitted Harley seals coated in wd 40 they still leek.3rd time Harley seals coated in a bit of washing up liquid still leeks.
All gasket surfaces thouroughly cleaned and deagreased manifold kept central tigtened down evenly.
Spraying with carb cleaner using the nossle has shown the leeks to be on both cylinders between gasket and cylinder head.I have run out of ideas I have checked carb diaphram and voes pipe all ok no cracks in the manifold that I can see.I evan was beginning to think maybe the chemicals in the carb cleaner had some wierd effect so I sprayed other peoples bikes and no change in the idle speed.
Any advice or suggestions welcome I have run out of ideas and getting to the stage that I am going to coat everything in silicone hate to do it but we dont get much of a summer here in the uk and I need to ride my scoot.
Thanks
Rick |
Kilroy
| | Posted on Wednesday, May 28, 2008 - 12:05 pm: |
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Are you sure that when you spray carb cleaner around the intake seals you are not sucking some of the vapor in thru the air intake? A little backfiring / popping is not unusual on these motors when you let off the gas, especially during engine braking. That being said, you have to make sure that intake is positioned correctly - as you know it is not easy to fit and even harder to get the bolts in the right way. |
Ricardoblack
| | Posted on Wednesday, May 28, 2008 - 01:28 pm: |
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I have sprayed the carb cleaner with a nozzle attatched so you can direct it quite accurately .The main leeks are between the gasket and the head .Everything was thouroughly cleaned before assembly.I can't understand it I have been through all the posts I can find.The bike is not nice to ride pops and bangs hard on closed throttle surges on neutral throttle coughs through the carb.
I am starting to loose patience .I'll have another go at reasembling it and if it still leeks that liquid gasket is going to get used.
Rick |
Al_lighton
| | Posted on Thursday, May 29, 2008 - 09:26 am: |
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As the engine heats up, the cylinders grow vertically by a substantial amount due to thermal expansion. As since they are in a V configuration, they grow further apart at the intake manifold level. The intake manifold does not grow as wide as the cylinders move apart from each other.
The seal surface on the manifold is a smooth machined surface that the seals move on during this expansion. You need those surfaces to be smooth and greased with seal glide for their sealing to remain intact during expansion.
You don't want to check for leaks with degreasing agents such as contact cleaner, brake cleaner, carb cleaner, etc. You'll end up stripping the seal glide and making the surface stickier. And some chemicals will attack the seals themselves, making them gummier and less likely to slide easily, which will guarantee leaks. Water works to check, but a propane torch with the nozzle on low (and no flame, of course) works better.
You final solution of liquid gasket is doomed to failure. Thermal expansion is one of those irresistible forces of nature. The expansion will still rip a hole in the seam. Those seals must be allowed to float to do their job.
Lightly polish the machined surfaces on the manifold, and lubricate them well with seal lube, and don't strip that lube by using degreasing agents when you check for leaks, and you'll have the highest chance of success. |
Blake
| | Posted on Thursday, May 29, 2008 - 11:40 am: |
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You don't want to check for leaks with degreasing agents such as contact cleaner, brake cleaner, carb cleaner, etc. You'll end up stripping the seal glide and making the surface stickier. And some chemicals will attack the seals themselves, making them gummier and less likely to slide easily, which will guarantee leaks. Water works to check, but a propane torch with the nozzle on low (and no flame, of course) works better.
New information that is greatly appreciated! Thanks Al! |
Ricardoblack
| | Posted on Thursday, May 29, 2008 - 02:12 pm: |
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Many thanks for the new information Al.What would you recommend as seal lube ?I have tried WD40 and washing up liquid so far without success.The Wd 40 seemed to be the most effective but in one of the posts on this subject someone warned against it due to chemicals that may dry out the seals.I havn't tried petrolium jelly maybe I'll give that a go....And lightly polishing the machined face on the heads.
Thanks
Rick |
Ricardoblack
| | Posted on Thursday, May 29, 2008 - 03:15 pm: |
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Hi
Please don't take this the wrong way ,I am trying to understand how this works.I understand how lube is required so that everything can settle in position without rips or wrinkles in the seals but I don't see how any lube can last for longer than it takes for the bike to get up to full temp.The engine temp and the washing effect of fuell will surely remove anything fairly quickly.Also the nature of the manifold clamp with its taper once tightened down will cause the seal to stick.
The heat generated by the head and the rubber seal will inevitably stick to each other.I would have said that because the interface between the manifold and head was rubber this allows for the movement caused by expantion.
I don't know if I have explained myself clearly it is the floating aspect you mentioned that I find difficult.
Again please don't take this the wrong way nothing I have tried has worked and I welcome any suggestions just trying to understand how this works.
Rick |
Buell_bert
| | Posted on Thursday, May 29, 2008 - 04:51 pm: |
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I would try SIL-GLYDE it is sold in most any auto parts store and has many uses especially rubber parts lubrication. I have used it for years. Hey just my 2 cents worth. Oh it comes in a tube and a little goes a long ways. |
Al_lighton
| | Posted on Friday, May 30, 2008 - 12:19 am: |
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That's the stuff.
Those surfaces are always moving relative to each other during engine heating and cooling. The design of the manifold and seal is supposed to allow for that movement. That's why polishing that manifold surface prior to reassembly isn't a bad idea.
If there wasn't movement, they wouldn't be designed like that. There would be an integral flange on the manifold and a flat gasket between the flange and the cylinder face. But if you put a V engine together like that, you'd probably split the metal. Thermal expansion will do amazing things.
I've always questioned the wisdom of the steel bracket on the older tube frame models that bridges the two cylinders (the one that the upper central heim joint tied to). It seems like it would be guaranteed to twist the cylinders as they heated. There's probably more to it than meets the eye that I'm just not seeing.
Al |
Ricardoblack
| | Posted on Friday, May 30, 2008 - 08:07 am: |
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Hi Al
I do understand what you are saying ,I just don't see how you can stop the seal from sticking.Every piece of rubber on a motorcycle evan after one heat cycle requires prying loose including the manifold seals (I know your going to say thats why mine don't seal)Any coating will not last long ,short of teflon coating the gasket faces.Hot metal and rubber just stick.
Again please don't take this the wrong way.I very much appreciate you trying to help and I will be polishing the gasket face and trying again today.
Rick |
Buell_bert
| | Posted on Friday, May 30, 2008 - 12:30 pm: |
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You can ask AL but try the SIL-GLYDE the rubber will not stick and will last thru many-many heat cycles, maybe forever (just kidding). It does not wash away or run and lasts thru a wide temperature range. I use it for rubber O-ring and auto hoses for easy removal later and metal to metal mechanical brake wear points . |
Bluzm2
| | Posted on Sunday, June 01, 2008 - 11:06 am: |
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Note to self...
Pick up tube of Sil-Glyde.
All thanks for the tip, you are ALWAYS a source for great knowledge.
Brad |
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New Intake seals won't !!!Help