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TIme to deep clean my carbs?

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My 250GT is developing a problem. It has a fully stock fuel system and exhaust. It starts well on warm days, and fairly well on cool days. The choke has a very noticeable effect on RPM, and keeps things at around 2500 RPM once the engine has started.. Full speed operation is normal.

However, the bike has a bad habit of dying at anything less than 2K RPM. Once it dies, it won't relight until it's been sitting for a while.

The last time I dealt with this, after it died, I tried holding the throttle open and winding for one or two bursts, assuming I needed to clear flooded cylinders. I then applied the choke again and cranked two or three bursts, but there was no kick. I then pulled a plug and found completely dry, nice light tan plugs.

Do I need to open the carbs up and clean them? If so, what parts should I have on hand before digging in? Bikebandit doesn't seem to list a separate rebuild kit, as many other engines offer.

Basscliff's rebuild PDF lists a set of O-rings. Will they work for the 250?
 
More likely you have tight valves

What maintenance have you done?
 
Not much recently. Point taken about basic tune-up as a starting point.
 
Yeah, start with the valve adjustment, see what results you get

Then, clean the carbs if needed - full clean per the tutorial

Sync the carbs and check the timing

I'm not real familiar with the 250, I'm assuming it has electronic ignition?
 
Yeah, electronic ignition. I checked the valves as suggested: They were perhaps .0005 tighter than spec. I readjusted them to .001 to .002 on intake per Haynes. Carb throat seems VERY clean. I removed the carb-to-cyl head boot, and the intake O-rings are shot. Ah HAH! I've got new 30MM O-rings on order from Mr. Barr.

BTW, neither Harbor Freight, not AutoZone, nor Heyser Suzuki in Laurel can supply ignition wrenches! I just carefully gripped the adjuster with pliers, but I think I'll whittle my own 3mm open-end wrench before I try again. (I noticed that even the Haynes manual photographed themselves using a loose fitting 9/64" instead of a metric wrench.)

Also, where can I get this tool?
2013-11-01_204052_zpse25fbdf3.jpg
 
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Now now, My Haynes manual has been with me for many years. Thank you VERY MUCH for responding, though. I was reading the stem-to guide clearance rather than the valve clearance. Haynes had it right; in fact, they had it right in two places.

I am VERY glad I got this message before I started the bike. (I'll bet the O-rings will also help).
 
Well well. Valve lash adjusted to 004", intake O-rings replaced, and everything put back together.

I'm afraid I still need to take the carbs down all the way. The bike now cold-starts with full choke easily, but it stumbles when I open the throttle. When it is fully warm, it dies, choke or no.

Almost the precise opposite of the problems I was having originally. Any thoughts? (And thanks for the quick responses!)
 
Definitely sounds like plugged pilot jets to me. Time for a carb cleaning! Feel lucky that you only have half the number of jets and other tiny bits to worry about. :)
 
Clean and sync, as I said

The throats being clean means nothing. Only air goes thru there. There's lots of tiny passages in the carb body that get clogged up.
 
OK, carbs coming apart. The brass parts are coming out easily.


One question: I hear that carb dip will tear up O-rings. When I dip the carb body, what about the seals on the throttle plate shaft? Should I pull the throttle plate & shaft? There's no mention of the throttle plate in Ed Ness's PDF.
 
this is how far I took mine apart

P1060225.jpg


P1060230.jpg


P1060229.jpg


and

P1060244.jpg





and if you can.....get new O rings......one less thing to worry about when you go to put them back together....

.
 
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Ooops!

Ooops!

Gatekeeper: Yes, I have Bob Barr's O-ring set plus the intake 30MM o-ring. All was good except the choke O-ring, which was too large. I'll use the old one there.

It looks like there wasn't a varnish problem, but there was 30 years accumulation of EXTREMELY fine rust particles. Things look much better now.

Unfortunately, as I was putting the second carb back together, I noticed a 1-cm hole in the throat. I immediately went back to the other carb, and, sure enough, there is a 1-cm aluminum plug topped with a flat rubber washer (#16 in this image: http://d136nqpz68vrmx.cloudfront.net/schematics/schematics/suzuki/suz008/SU0068_013.gif). The plug itself is not listed in the parts breakdown!

I probably blew the plug to Kingdom Come as I was air blasting the rinsed carb body. I'm surprised I didn't notice an aluminum bullet shooting out of my hand, but it went somewhere.

I have a lathe, and I can whittle a new plug, I suppose. I could probably get away with filling in the hole with epoxy or JB Weld. Any thoughts? Is this some sort of backfire pressure relief?
 
mf70 said:
Is this some sort of backfire pressure relief?
Click to expand...

That orifice was necessary to machine the carb body. It most definitely needs to be sealed. The O-ring on top simply helps to seal it and keep it in place.
 
You should be able to just throw the carbs in the dip once disassembled. No concern on the shaft seals but be careful and don't put any of the choke plungers or the choke shaft seals into the dip. It will destroy them. With that said, I like to throw anything in that I need to remove the O-rings on with the O-rings still attached. Things like fuel connectors, float seats and such. Makes getting the O-rings off MUCH easier.;) Don't dip anything that looks like rubber that you need to keep. I disassemble the slides and clean the needle parts separate from the slide/diaphragm assembly.
 
Well, I whittled a new plug.

P1011188_zps7d84f07d.jpg

I sure wish the "howto" warned that there was a plug that would drop out. I assumed that the disk was pressed in like the cover over the mixture screw, not gently resting on a subtle ledge. And the part wasn't even available!
 
Seems like some are pressed in and some rely on the O-ring and pressure to keep it seated. I have several sets of carbs that have no loose plug and no way to put an O-ring between it and the gasket. I have had other carbs that the plugs did fall out but those seemed to be more recessed then the ones that need the O-ring. Can someone verify that some carbs didn't need the O-ring between it and the float bowl gasket? I've tried to remove them and they just seemed to be pressed or staked in place.
 
Back on the road again!

Back on the road again!

Just a couple of "oopsies":

#1: In spite of Mr. Haynes' warning, I lost the choke rod detent balls. Fortunately, they don't actually have to be spheres, so I cut off two finish nail heads to provide the needed tension above the detent springs.
After assembling the gang of two,
P1011189_zps6528be8a.jpg


#2: I realized I had two hoses left over. Some cogitating showed where they plugged in (slightly complicated by the fact that they plugged in to different places on each carb).
Fitted it back on the bike, rigged up an "IV" using this:
Measu-funnel_zpsc39737a8.jpg
Only catch is that is has a mesh screen above the shut-off. The gasket can't seal against the mesh, and gasoline seeps right through. Without the mesh, everything works perfectly.

Got it running, and synch'd the carbs:
P1011190_zpsefd92368.jpg

... all good!

Assembled the tank & seat, rode away, and...

#3: Died .5 mi from home, at the bottom of a 200' hill. Nothing would light it. Pushed it home, set it up to store, and commenced cleaning the workbench. Hmmm, there's the fuel line spring... Oh! The fuel line needs to be connected to the tank!

Actually attached the fuel tank to the carburetors, and, mirabile dictu, Suzi runs beautifully. What a way to end the year.

Thank you all for your input!
 
have you tried the fuel tap assembly; cleaned the filter; is the vacuum pipe and spigot in good condition; not too short or kinked; when you suck on the pipe does it open the fuel tap and allow fuel to flow;
take out the drain plugs from the carburetor bowls and see whats in them; hopefully they'll be clean whilst they're out i turn the fuel tap to prime and let petrol wash through unhindered for 15-20 seconds to 'maybe' wash out any foreign 'stuff'
are the petrol lines of the correct grade for fuel lines; some rubber/plastic/synthetic hose can be and is broken down by petrol and deposited in the carbs; if this is a problem then you will have to strip and clean the carbs ;
it sounds like your not getting fuel through and wonder if you have a damaged float; sticking needle;
 
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