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Just as expected..going on a trip tomorrow on the 74 R75/6.

Had rebuilt carbs, valves clearances checked and tweaked, points gapped, timing checked - spot on, carbs synce'd and ready to go...NOT

Out for good long run yesterday make sure everything ready to go but high idle after good warm up. Did usual check to see if advance unit was culprit..nope...new springs ordered from Motobins as back up but advance unit working fine.

Hmm...had to be air getting in somewhere...sure enough right upper carb air intake was split up by airbox clamps (lower one)...ahaa...air pouring in through here. If tighten up clamps too much it just widens the split. Guess I cracked lip on carb installation...not taking the required beer before assembly obviously...damn...nearest dealer 250kms in opposite direction to trip...so what to seal up with???

I've used Black RTV sealant (gasket silicone) in the past and got me through a jam...any other ideas that might work?? Gonna be gone couple weeks... maybe spot a BMW dealer Stateside and see if can get one is other possibility.

Radiator hose if I could find right diameter?? Also thinking if I could find right plumbing rubber connector...kind you see at plumbing/hardware store to join two pipes together with clamps..might work if went over top of existing air tube and coupler? Heavy guaged PVC bag to wrap around and help seal?? Condum...oops don't have any around...I'll check with the young lad see if has a few extras for the old man!

Any other "quick fixes" or suggestions out there??

PS: Our group consists of my 74 R75/6, me friend John(boy)'s 72 R60/5, buddy Chris' 76 R90s and a rogue Brit Classic (maybe) 62 Norton Dominator...should be a hoot...always is! Pix will follow someday on return.

That Black RTV should work...or the product called Plumbers-Goop...works for nearly anything that does not have to withstand pressure. Just be sure it has time to cure before "use"...about 4 hours! Overnight is best.

An air leak before the carbs shouldn't be responsible for the high idle, should it? You could run the bike with no filter (aka K&N filter...ooops...did I really say that!)...and it shouldn't really make a difference in the short term. Now if the connection from the carb to the head were leaking, that's a different story.

Kurt in S.A.

Tape.

And, I agree with Kurt (big surprise). So, there may be another problem.

You're right...stupid of me! However, between RTV sealant and duct tape I fixed the upper leak which...led me to the "real" problem..another leak at the carb/head joint...which was the real culprit as you have pointed out. That's gonna be harder to seal up. Thinking I might try "red" hi temp sealant there as it gets pretty warm in thse parts. Once that stuff sets up it might do the trick...the saga continues...

I'm sure this is the problem but if not Its gotta be the advance mechanism. I ordered some new springs from Motobins but won't be here for departure time..thought I could steal some from another bike but I think the 74 R75 springs were shorter than the later models?

Just looking up BMW dealers on our route and maybe order new parts for pick up along the way..

Dont use radiator hose - DAMHIK

Some Jap cars have a hose between the filler cap and the tank which is the right size and material and wont cost much if the wrecker lets you take it off yourself.
They are designed to last the life of the car so they stand up OK on airheads.

Maybe a local auto parts place can sell you a NEW correct diameter and thickness radiator hose that you could slice up.
That's what the OE ones are made from.

Radiator hoses are designed for antifreeze and water. The carb-head connectors are designed for gas and air. Are they really the same?

Kurt in S.A.

Kurt in S.A. wrote:Radiator hoses are designed for antifreeze and water. The carb-head connectors are designed for gas and air. Are they really the same?

They sure look EXACTLY the same;
I'm gonna check on what's available next time I need some.
The problem is that cutting them as square and as cleanly as the factory ones might require some improvising.
Radiator hoses are gas proof, and they're usually surrounded by air on the outside, so that makes them 'airproof'.
and they're built for more heat and pressure than our intakes will ever see.

Gonna try the high temp RTV sealant as it gets pretty hot there. Its not a big opening but definitly that's where its leaking. Sprayed some WD40 at it and definitly a leak. I'm just cleaning up split tonight and red RTV so can cure over night. Get it on early tomorrow morning and hope it works. Interesting to see how long it holds up.

Rad hose, if can find the right inner diameter size might work, but sounds like a concern??

Give it a flogging tomorrow to see how it goes...if not...well the ol' GS it is then. Thankfully I have a back up.

Thanks for the ideas.