TIme to deep clean my carbs?

[mf70]

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?

[Big T]

More likely you have tight valves

What maintenance have you done?

[mf70]

Not much recently. Point taken about basic tune-up as a starting point.

[Big T]

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?

[mf70]

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

[Nessism]

I checked the valves as suggested: They were perhaps .0005 tighter than spec. I readjusted them to .001 to .002 on intake per Haynes.
[ATTACH=CONFIG]37258[/ATTACH]

Your valves should be adjusted to .003-.005".

Factory Suzuki manual here...http://members.dslextreme.com/users/bikecliff/
Throw that POS Haynes in the garbage.

Motion Pro sells those valve adjust tools. Google will shake them out...

[mf70]

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).

[mf70]

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!)

[eil]

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.

[Big T]

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.

[mf70]

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.

[GateKeeper]

this is how far I took mine apart







and






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

.

[cowboyup3371]

You don't need to worry about the throttle plate shaft

[mf70]

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...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?

[GSX1000E]

Is this some sort of backfire pressure relief?

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.