Does the GS discussion forum .... include the Suzuki GR650 twin bike ... or where?

[phydeauxmutt]

I put in new plugs ... at 1st standard heat range and later the hotter plugs.

What was the inspiration for the hotter plugs?

Hopefully you realize that the plugs do not control the heat in the engine. That is, rurnning a hotter plug does not give you a hotter spark. The heat range of the plug relates to its ability to shed heat. You should only run a hotter plug if you have oil fouling and need to burn them clean. Actually, it's better to fix the problem and run standard plugs, but a hotter plug will get you home.

As the weather temps get colder, it is getting harder to start the 2 cylinder engine. I pull full choke and only get a feeble idle at first. Can't open the throttle as it kills the engine. About a minute of running full choke the rpms come up slightly and I can rev up engine slightly without killing it. I then ride it carefully around the block holding full choke with my left hand ... as the choke lever will NOT stay where I put it. Finally, the engine warms up to make a few HP and I can start my ride, but can't yet get to good rpm ranges. Today I must have rode 3 miles before the engine developed full power and acceleration .... at choke OFF position. I am afraid as the temps get colder, I won't even be able to get a start (at full choke). Last summer .... all was fine for starts but was still COLD blooded!

Any suggestions on carb settings, etc .... to get this engine not to run so lean?

Before you change any jetting, ADJUST YOUR VALVES.

One of the classic symptoms of tight valves is hard starting, especially when cold. Check your clearances, adjust them toward the upper part of their range. I'll bet that will be about 80% of your problem.

Yes, bikes of that era did run a bit lean. You have unlikely seen the mantra: CLEAN YOUR CARBS. Since the bike has been running for a couple of years, the carbs might not be all that dirty, but might benefit from a slightly richer pilot mixture. Try turning the pilot screws out about 1/4 turn to see what happens.

[dennco2]

I was hoping the hotter plugs would produce hotter spark .... in colder weather. The standard plugs looked fine.

I had the valve cover off and checked clearances ... last summer. One exhaust valve needed a bigger shim than what was in there, so I put it in there. Now I am wondering if that was enuf, as I still get an occasional popping sound from that cylinder. When I last adjusted the 2 pilot mixture screws, I turned them out 2.5 turns from fully seated. Another half turn OUT will make the engine run richer?

[dennco2]

Here is an updated pic of my Suzuki GR650 Tempter ... with rack and back rest and milk crate.luggage rack & milk crate.jpg

[Big T]

I got my eye on a 36 year old 650 Tempter for sale. As far as I know there is nothing wrong with the bike ... but if I get it I will want to get a back rest and large luggage rack for it. I don't see any accessories for that bike due to limited 1 year production ... and I am wondering if I can adapt a back rest and rack from another Suzuki model?? Direct fit ... or decent looking retro fit?

Thanks for any help to solve this dilemma!

Where? In "other" questions, a subforim for non GS bikes

[Nessism]

I was hoping the hotter plugs would produce hotter spark

Nope, that's not how it works. Hotter plugs are just that, plugs that run hotter...so they burn off deposits. They have no impact on combustion temperature in of themselves.

[dennco2]

Update on my Suzuki GR650 twin. I rechecked my settings on the mixture screws and had to adjust them again ... out to 3 full turns from closed. The engine ran soo much better. Running lean created an occasional popping sound (like mild backfire) and the left cylinder would not fire for the first minute after start until engine warmed up and only with FULL choke. It still doesn't like to rev up past 5K but produces plenty of low end torque, so I don't care as much.