Yeah, sorry, there's a lot going on...srankin wrote: ↑Tue Nov 12, 2024 7:26 pmI am kind of loosing track of just what you have done and are having problems with, sorry, it its this method of communicating.
When you put the twist grip back together are you sure you lined up the chain gear and grip properly. There are timing marks on them. If you did, any take up will be at the carb barrels. The trick is to take up as much slack as possible yet still let the throttle sit on the idle stop when turning the handlebars. This is dead set first thing to do because if you have any upward movement you won't be able to adjust idle. Visually, when you have then set, you can see as you slowly twist the grip the two throttle levers move. Set them visually so they both move at the same time by taking up or reliving the barrel adjustment. Even better yet is to have a carb sync tool but it can be done by eye and ear.
I would not worry so much about the butterfly shaft, if it is worn or the seals are bad, spraying it with something will seal the vacuum leak and idle will change. No change means there is no problem. Like I said earlier in a post to you, it takes a lot of mileage to wear out the shaft and o-rings. They are pretty bullet proof.
As for the exhaust, your bike should have a cross over in the front of the engine and behind the engine, a one crossover set of pipes is either from an older model bike or aftermarket. In the past there were issues with some of the aftermarket header pipes not fitting together well, Mac being the worst. Before each muffler there should be a clamp to clamp the muffler to the header pipe. No clamp no seal.
Admittedly, from my experience the stock two crossover pipe system can sometimes be a pain to reinstall after being removed. However, BMW went to the two crossover system to improve low end torque and balance of exhaust. Who know why it was switched out to a single, but it was the wrong thing to do as far as I am aware.
As for discoloration, yep, airhead headers don't stay chrome, They get hot and depending on the chrome used in manufacturing will most likely turn dark blue or yellow, Road crud will also add a bit of character to then as well. I use simicrhorme polish on mine and they so far have stayed blue, shows I ride the bike LOL.
Keep up the good work, St,
On the exhaust, it's a stainless--and therefore I believe an aftermarket--set. Whenever I remove it to sand and polish the headers, I may just add slots and clamps on the crossover (only one) to perfect the seal at that point. No big rush unless after the carb refurbishment it contributes to rough running. I'll try cleaning up the sealing rings at that point to save the $40.
For now, there's just a subtle 'clack-clack' from the small leak where the header joins the exhaust port (and which people often mistake for tappet noise). So long as it's small, it shouldn't affect sealing sufficiently to endanger the exhaust valve--but I won't let it go for long.
On the throttle grip: I had noticed the indexing marks (thank you) but evidently didn't get the little notch that separates the cable's casing from the chain just right or something... at any rate, R&R'd it again, took the remaining freeplay out at the adjuster where the single cable merges into two... now it's perfect. Very light action, immediate and crisp return, very small freeplay rotation at the grip. Feels as a new bike's throttle would. Love, love, love those GT grips in my hands.
On the carbs: the more I thought about 40-year-old O-rings and gaskets in there--and needles with 64K on them--the sillier (or lazier and cheaper) I felt, so removed the L/H carb this morning to soak it in Berryman's overnight.
Attached are photos of badly deteriorated O-rings and gaskets. The throttle shaft O-ring was indeed the only one that looked as if it might have been sealing properly--or closer to it than the others. It at least had some elasticity left, whereas the others had close to zero. But if you zoom in on the close-up of the removed O-ring, you can see it, too, has aged sufficiently to have a wear groove around its circumference...
The others were unquestionably toast: flattened, hard as a rock, distorted, torn... including the idle mixture and main jet O-rings, so those alone could explain the imperfect running. The enricher gasket was brittle and very likely passing air into what I gather is a carefully metered air/fuel mixture for startup. That would explain the slow-to-start behavior.
On the penultimate photo, there's an embossed number on the butterfly, so no need to make marks on it to get orientation right, as I've read. Also, no need to Dremel the butterfly screws, as some do: the peening is very subtle, and they back right out.
If you want to peen the new screws rather than use loctite, the method is to place a brass or aluminum rod on the anvil portion of your vise, align the plate and tighten the screws, then set each screw's head on the rod for peening to avoid bending the throttle shaft or ovaling the carb body's hole.
You can get one carb's components in the basket, then slip the carb into the can on its side under the handle as you lower it in, to soak one complete unit at a time.
Mañana I'll do the R/H carb, and this weekend we'll see what's what.