Staintune on R80G/S & US/UK/Euro carb tuning.

Just got a '86 R80G/S with a Staintune pipe on it. With the airbox snorkels both on it runs REALLY clean and strong at low-mid revs but won't rev out, i.e it won't go beyond 70mph indicated in top. It just stops revving. At a guess the bike is only about 2/3's through the rev range.

With various combinations of the snorkels i.e. one off one on, facing in or out, either side removed or both off etc I can get it to rev out, but it's very 'woolly', not very strong and it's feels like there is a definate disconnect & delay between the throttle and motor at all revs.

I'm guessing this behaviour indicates not enough air at high revs with both snorkels on, and too much all the way through with one of both off? According to the Staintune website their pipes are to be fitted with factory carb settings.

I haven't had a chance to pull the carbs yet and check the jet sizes and needle positions but do have some questions about the differences between US/UK setting as in the Haynes manual:
My bike is ex Europe, so it should use the UK carb settings?
Haynes lists some significant differences between jet sizes between US & UK, is that because of the different compression pistons?
Which setting are best?
and finally:
does anyone have any recommended variations for Staintune or are factory standard settings best.

Thanks
Eddie

Leave the snorkles alone .
Plenty of reading about this on Snowbums .

Float hieght
Timing advance
Air filter dirty
Plugs and/or leads breaking down at high load
Have you given it a complete tune and service ?
Yanks had leaner jetting because of thier EPA bullshit

It wont be the snorkles




.

I'll second that!

What kind of airfilter are you running and what is its condition?

yeah, all that-- and I'd add check those carbs over thoroughly.

That high part of the throttle range is main jet, right? float heights will ensure you've got enough fuel flowing.

I know I keep playing this note, but that really does almost sound like pinholes in a diaphram.

anyway thats going to be my stock answer from now on, just in case.




I put a staintune on my PD, and it doesnt change much except the final sound- so yes, I'd stick with stock settings.

If you give me your carb #'s I can double check the settings later tonight. Sometimes Haynes/Clymer is a little wonked.

Definately check the diaphrams!

Thanks Folks

Diaphrams have been replaced in the last year by PO, I have the old ones in the box of spare bits.
Air filter is stock, not perfectly clean but not far off. Definately not what I would consider dirty.

Playing with the snorkles was the easiest thing to get at while riding it to work, weather and other priorities has meant I haven't had a chance to do a strip down on it yet. I'll pull the plugs this weekend and check those, plus check the jet sizings and needle heights.

Float height and Timing I will have to do some reading on as I've not had to look at thost before and so don't understand how to check them.

I forgot to mention, the bike had been sitting unused for at least 6 months before I got it.

Dump some Seafoam in the gas.

Check the diaphragms.

Ride it about 1K and report back. If it sat for 6 months, it's mad it was ignored. It just needs some tough love. Ride it like you stole it.

You may want to manually push the slides all the way up and see if they drop down smoothly, or pehaps bind on the way up....

Eddie - sitting for six months shouldn't be a problem.

Since diaphrams and air filter appear to be in decent shape, time to look elsewhere. It's possible the Main Jet O-Rings are in need of attention, or that trac is in need of a thorough cleaning.

Float height may not be right, but I wouldn't suspect that in this situation - normally the floats as they age get heavier and allow more fuel in the float bowl. I wouldn't expect them to shut off the fuel at a lower level. Somehwere on this forum recently someone gave a measurement for fuel level - something like - it shouldn't be any lower than a .5 inch below the lip of the bowl. Normally the floats get adjusted by turning the petcock on while holding the float up. Then slowly lower it. Fuel should flow when the float is paralell to the carb/bowl junction. There's a seam on the float, use that for alignment purposes.

Another place to look is the fuel filters, most likely in the petcocks. But they could be in the tank.

Another possibility is the exhaust system - perhaps a mouse crawled in there and is now plugging the works.

As far as the ignition timing, I doubt it changed so drastically to cause your symtptoms. But you could have some poor connections at the coils, or have a low battery. Spark power goes way down with only a small drop in voltage.

:) PO replaced it with an 1150GS, he was busy riding that.

Seafoam? Haven't heard of that. Maybe it's something we don't get here. The bike was stored dry, I put new gas in it to take it away. I've done about 60 miles on it so far.

Will try that, Throttle moves a full 1/4 turn and is quite heavy and very slow to close as it something is binding on the close, I had suspected this was in the handlebar throttle mechanism but need to check it further. Opening is heavy but doesn't feel like it is binding.

When I tried the different snorkle combinations I could get the bike to rev out, just not cleanly and strongly, very weakly.

Fuel filters are inline in the fuel hose either side of the airbox, They are see through and look clean to the eye. I'm not sure if others are in the petcocks. The tank is a 100GS unit and I can't see anything in there.

Stranger things have happened, it would have to be a small mouse though. The opening is smaller than the factory pipe on my old G/S. I suspect it wouldn't run very well at all if anything was in there.

Likely the cables themselves. Those are teflon-lined cables and if the PO lubed them even once, they're irreversibly toast. Lubing teflon makes the latter swell, thereby gripping on the cable.

You can lube them, but not with petroleum products. There is something safe to use, but don't recall what it is.

Fuel filters are inline in the fuel hose either side of the airbox,

These in line filters can restrict the flow enough to prevent redlining the bike. But if removing the snorkles helps it rev up, it makes me think it's running rich - quite the opposite of plugged filters. It's possible the fuel level is too high in the float bowls.

Time to systematically look at all systems on the bike and handle what comes up.

So I've had a bit of a look this evening and found a couple of things.

The carbs are 64.32.305 & 306, with 135 main jets. According to Haynes these are fitment for pre May '83 G/S and should be fitted with 145 mains for a UK bike and 150 for US. Later G/S bikes had different carbs with 135's fitted but apart from the numbers I have no idea what the difference is.
If it helps the engine number is ZSA 063312.

I couldn't figure out how to get the needle out of the piston to check which position that was sitting in. I also couldn't pull the plugs as I didn't have a plug socket the right size.

The airbox was interesting, can someone advise whether the piping in mine is UK standard or has some of the US emmisions? particularly the pipe and swirl mechanisms that extend into the carb tubes, my old airhead didn't have all that so I haven't seen it before.

The black hose exiting the front of the airbox chamber goes straight across the top of the motor/starter under the top cover to the front of he bike somewhere.
I'm tempted to go out tomorrow (It's night here now as I'm GMT+12) and get some 145 mains and chuck them in to see what happens. I was going to be going to the dealers anyway to check out some other stuff.

Is that the engine # stamped just above the oil dipstick ? or the # on the raised rectangular section on the very bottom of the block on the left side ?

engine # is stamped above the dipstick and should match the frame #
*EDIT* IE 01/86 6286767 to 6287429
Shit had a brain fart ,mono #'s don't match .What is the frame # ?
Your #didn't match anything in my records .

The pipe work in the airbox connects to the reedvalve engine breather on the top right of the block and is normal .

Hey, thanks for your help.

Frame number is 6256033 but apparently 2 owners ago the motor was changed as the original one failed. I don't seem to have details of the original motor #.

Engine # was taken from the raised area, there is nothing above the dipstick.

Just found this: http://bmbikes.co.uk/chassispages/enginechassis800.htm
which indicates the frame is Jan '82, a few years older than I thought as it is taxed as an '86.

Looks like I might have written the engine number down wrong though, will check that tomorrow.

yah, my book says 145's for the main jets, as well. Bing says those carbs are for an R80, and excludes the GS. dunno bout that.

unless Im looking at the wrong hting, the needle should be accessible by removing the carb top, then the slide. If you look down the tube on the slide, there should be an aluminum flathead screw.. remove that and the needle top with a circlip should be under it.
Oh, and bing says it should be in position #4. Which is the bottomest one.
Yor needle jet should be a 2.64 and and the jet needle a 241.

as FR700 said, all that piping is normal I'm pretty sure, most of it is crankcase breather stuff.

Here's a photo of the slide and the needle and screw. Hopefully this looks like yours.

"The airbox was interesting, can someone advise whether the piping in mine is UK standard or has some of the US emmisions? particularly the pipe and swirl mechanisms that extend into the carb tubes, my old airhead didn't have all that so I haven't seen it before"

Yep! that's standard UK setup for the pipework and tubes.

Heres a pic of mine without the smaller tubes fitted:-