550b wont rev

[little blue]

I have a 550 b that wont rev past 5k, carbs (slide type) have all been cleaned out, timing checked but it still wont go!....any ideas?

[Ironriot]

A number of things. An air leak for one. Also have you checked the cables? Maybe they're out of adjustment? Biggest thing though would probably be air leaks somewhere in the system. Particularly the O-rings behind the intake flanges. Are you running the stock air box and filter? Hit us up with a bit more info. I'm sure the more knowledgeable people will chime in sooner or later.

BTW adding in what year your bike is in your signature and other information will definitely help

[little blue]

I am running a stock airbox, i have put extra sealent on the o rings to see that would help also the idle is very erratic the, valves have been checked and re shimmed, i am running a 4-1 but have got hold of a standard set of pipes which i will try and get put on over the Christmas holidays
hope this helps

[hampshirehog]

Could be fuel or electrics (or something else). Well that narrows it down then!

To help people help you out can you give a bit more detail. Does it tickover ok, run on quarter / half / full throttle ok or does it just all fall down at 5k?

My immediate instinct is the opposite of Ironriot 's and instead of running weak you're running rich - but without more info we're both guessing.

Wally

[little blue]

After a run the plugs are a nice colour. the motor revs quite nicley to 5k then just coughs and splutters it is also quite difficult to start when cold!

[Nessism]

The mixture may be lean due to air intake leaks and leanness from the header. Even at that though, the bike should run better than you describe. Could be ignition related. The plug caps sometimes fail as do the coils. Make sure all the header pipes are hot indicating they are firing; you may be dragging around a dead cylinder and not know it. Another thing to check is the spark advance unit – the weights should move freely (I think you can check by rotating the points cam with your fingers).

Going back to the carbs, they need to be spotless and properly sealed (new o-rings inside the carbs and on the intake boots). Many many newbies don’t go through them thoroughly enough and wind up having to go back a second, or third, time.

Good luck.

[Steve]

... it is also quite difficult to start when cold!

This is a classic symptom of mis-adjusted valves. Adjust the valves and try again. It appears that one or more valves are too tight.

I know it won't help much at 5k rpm, but a good carb sync just helps general operation and smoothness, so you might want to do that, too.


.

[little blue]

thanks guys I will try all your suggestions and let you know how i got on
Thanks
again
mark

[BassCliff]

Hey howdy hey!

Mr. little blue,

Let it be known that on this day you are cordially and formally welcomed to the GSR forum as a Junior Member in good standing with all the rights and privileges thereof. Further let it be known that good standing can be improved with pictures (not you, your bike)! :-D

Thanks for joining us! There is a "right of passage" necessary to get these classic bikes back to their former low maintenance, bullet proof glory. I believe Mr. bwringer said it best. (Note: Although this is GS850-specific, most of the information still applies.)

----------<quote Mr. bwringer>----------
Every GS850 has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting.

It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years.

It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

Intake O-rings (install NEW OEM or Viton only - common nitrile o-rings will quickly deteriorate from heat)

Intake Boots (install NEW -- these cannot be repaired)

Valve clearances (more important than most people think)

Carb/airbox boots

Airbox sealing

Air filter sealing

Petcock (install a NEW one)

On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)

On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.

Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.
----------<end quote>----------

The best carburetor rebuild procedure is located here.
For your electrical needs read the Stator Papers.
Mr. bwringer also has some great repair tutorials on his website.
Mr. robertbarr has lots of necessary parts for carbs and such on his website.
And yours truly has a few pictorial maintenance guides (oil change, valve adjustment, etc) on my little website.

If you can't find what you're looking for in the above links or by using the search feature in this forum, just ask. The collective experience here is nothing short of phenomenal.

Thank you for your indulgence,

BassCliff
(The unofficial GSR greeter)

[srsupertrap]

Mark,
The Mikuni slide carbs equipped on the late 1970 Suzuki GS's were extremely lean. The stock set up would normally take several minutes of choke before the bike was rideable.

First get the bike running & warm. 1) Eliminate possible air leaks by spraying carb cleaner were the intake boots meet the cylinder head and any other suspect area. A leak will be indicated by the RPM dropping

I would check the ignition spark next. Remove one spark plug wire at a time & insert another spark plug in it. Lay the plug on the cylinder head. Start the bike up and rev it out to 5K and verify you have spark all the time. Repeat with the balance of cylinders this will rule out or in the ignition wires.

If the bike has been sitting and you have rust in the gas tank a clogged petcock could be causing this symptom.

BR
srsupertrap

[little blue]

Thanks for the welcome greetings and all the info, sometimes on a cold winters evening in the UK working on these beasts can seem very lonley, it's good to know there are so many of us out there, you guys have been great!
Mark
Little Blue
P.S. will try and get a pic of my bike to put on