Revs to the sky in neutral; barely revs to 6k RPMs in gear

Local Yamaha dealer had my bike for 5 weeks and charged hundreds of dollars to sync and rejet my bike. It's got stock air box, but MAC 4 into 2 turn out exhaust now. Before taking it in I out new plugs and dynacoils on and it ran pretty well, but still needed a fine tune. The thing never wanted to idle and would either be too low and die or too high. After their work, the bike does now idle well, they claim to have put a "stage 4" jet kit in, which I assume they mean stage 3. With the clutch held in or in neutral it revs no problem, but going down the highway on 5th at 60mph it struggles to gain any more speed. It'll chug and act like it's either not getting enough fuel or a cylinder isn't firing quite right. The pipes were all chrome when I dropped it off with them, but now 2-4 are blued and get hot to the touch at idle, but header 1 is warm at idle Nd doesn't get got until revving the bike. They claim to have cleaned the carbs, changed needles and gaskets but for the fortune paid this is ridiculous. Anyone know what the issue could possibly be? All plugs are gapped and the wires fire as they should.

 

If they (or you) didn't put the valve clearances in spec before all that expensive carb tuning then everyone was wasting their time.

MAC pipes will turn blue (although they all should and evenly) because they're not double-walled pipes like the originals. Virtually all single-walled chrome exhaust headers turn blue (or at least discolor to some extent.)

The fact that yours haven't all "blued" is indeed an indicator that all 4 cylinders aren't behaving as they should. It sounds like they didn't properly set the float levels and/or didn't get it properly sync'ed.

But step 1 is to check the valve clearances and adjust as needed to bring them in spec. Because until they are, a good vac sync isn't going to happen.

 

They did do a valve check and put a couple in spec; I do trust they actually went through with that, although I checked them not long ago and they all seemed within spec to me. Either way, I'd say valves aren't part of the issue.

 

Don't assume. Check valve clearances. 20 minutes spent now will save you 20 hours of chasing your own tail.

When a mechanic finishes a vehicle, and it's still not running correctly, all of his work becomes suspect.

 

EDZACHARY!

The Dude is right, at least check them. "Tain't hard; I did a how-to. If they're OK, then they didn't lie and they move up maybe... oh two ticks on the "know their stuff" scale.

Which is not to say that float levels aren't about to bite them in the arse.

Quite honestly, they shouldn't have needed a "Stage Anything" jet kit to tune for the MAC system if you have the stock airbox. Ask them flat out whether or not they DRILLED HOLES in anything, and if so, WHAT.

If the answer is yes, then start looking for a "parts rack" on eBay so you can undo part of what they probably did and do it right, yourself.

 

After ruling out a valve issue. It sounds to me that your cold cylinder at idle is due to a lack of fuel on the pilot circuit, unless the exhaust is popping which would mean it is too rich. The gutless power/dropping cylinders issue is probably due to excessively rich main jets from the stage 3 kit. The stage 3 kit is for PODS, any real mechanic should know that. So if you are running an airbox it is starving for air. Try removing the airbox lid and see if it improves. I'd bet it does. If so take the bike back and bitch for them to do the job right.

 

No "ruling out" has occurred as yet...

You're right about the various "kits." F* that. Back in the day, various motorcycle magazines attempted all sorts of mods to "improve" the popular bikes of the day. My fav is the Cycle World "series" wherein they tried to improve upon the stock exhaust system on the SR500 and failed SO MISERABLY that the series of articles simply stopped and were never mentioned again. I was paying particular attention because I had an SR at the time.

The simple hard honest gee golly gosh it sux but whatcha gonna do bottom line is this:

Yamaha knows (and knew even back then) what they were doing. They had literally thousands of highly-qualified engineers all over this stuff. Unless you're a GD Formula One race shop, you aren't going to out-engineer them.

My point being, they made the bike perform well from 1000rpm to 10K rpm, and still keep the EPA happy. It took CV carbs and some very sophisticated airflow engineering to pull it off.

Yes, you can "improve" it--- BUT only in a particular RPM range. You can move the powerband up and down; but as much as you screw with it, a stocker will always run away from it, unless you're on the track and everybody is WOT all the time.

Again, he needs to ask the shop if they DRILLED anything.

(note: the above applies to a lot of modded bikes. I love nothing more than absolutely handing some GXRZY-whatever 1100 with a "pipe" (and silly invisible LED turn signals, guaranteed) his butt on a silver platter on my STOCK 550R. Improperly-modded bikes simply won't pull from nothing to 10K; horsepower be damned I don't have to shift. Bye-bye.)

 

Re: Revs to the sky in neutral; barely revs to 6k RPMs in ge

what fitz said, but just from the thread title, my thoughts were that you are too rich. that being said, the blue pipes indicate lean. but having two cylinders rich and two lean would cause the conditions you describe. suggest you explore the jet section of lens catalogue for tips and a jumping off point. from the sounds of it, you can do better than the guys you paid to f it up with just a little research. also check the float levels first though. if they are off then nothing else will work right.

and I would not recommend taking it back to them. they f'ed it up, there is no indicator they can make it right.

you can do this. it's not rocket science, but almost.

CN

 

The bike runs well up to around 5500rpms, then starts sputtering from the exhaust and chugging, until reaching about 7500rpms then the power surges back. The fuel/air ratio was enriched slightly, and I replaced two carb diaphragms from JBM industries. This still sound like a tuning issue? Or something else?

 

Something else.
I hate to jump on the piss party, but you are ignoring some really solid questions.
Valve clearances re-checked by YOU. Not hard to do.
Did the Stealership drill anything?

Maybe it is different in Iowa, but in Wisconsin (at least Milwaukee area). The yamaha dealers do NOT touch anything over 15 years old. Their mechanical training doesn't cover 'vintage'.

There are intelligent people here who have dealt with these bikes for along time and know what to do.

Ask questions.
LISTEN!

 

You can CHECK your float levels on the bike in 10 minutes.
Level on centerstand, they will be around 6MM lower than the float gasket.
(This is not how you SET them - you are looking for a uniform reading)
if they are at random levels, pull the carbs and set them right.

It would be more accurate to level the carbs by getting creative with blocks of wood or removing the rear shocks, lift the front tire.
Then look for the 2-3MM level.

 

Re: Revs to the sky in neutral; barely revs to 6k RPMs in ge

Valves are in spec. I did them before dropping the bike off at the dealership, and they verified the valves were correct before their attempts at tuning. I just checked the mixture screws and they are all 4 turns out. I imagine turning them in 1-1.5 turns could make a difference. Have to give it a shot a bit later.