GS450 long warm up time?

[normcoffey]

Hey all, I bought a low mileage, nice but non-running 1981 GS450T a few months back and after replacing the tires, rebuilding the carbs, oil/filter, etc.; now have gotten it running to put it on the road. Problem is when cold, the bike will start on the choke but idles very low and stalls if you give it any throttle. It seams to take 5 minutes before it warms up enough to ride it. Once fully warmed up it runs very well. Decent power although a little hesitation off idle until your up over 2,000 rpm. Is this typical, the long warm up? I've thought about re-cleaning the carbs as maybe they are still gummed up a little. Any insight would be helpful.
- Norman

[DimitriT]

Sounds normal to me.

My 550 was doing exactly what you describe. Recently I replaced the piston rings and got my compression much higher. Now it will idle after only a few minutes of warm up.

I think depending on how well you're tuned, it will take a bit longer to get a steady idle as it warms up, but don't expect it to be rock steady until it is fully warmed up.

[Steve]

If I remember correctly (and it's happening less and less frequently nowadays )
the only bike that was more cold-blooded than the 450 was the 425.

When you "rebuilt the carbs", did you take them completely apart and dip them overnight?
Did you poke a small wire through all the holes in all the jets?
Did you then blow out all the jets and body passages with spray cleaner and compressed air?
Did you replace all the o-rings? Including the manifold o-rings?
Did you do a bench sync before re-installing the carbs?
Did you do a gauge sync after installing the carbs?
Did you tweak the mixture screws for highest rpm?

You didn't say anything about "dip". If you need to buy a can, it's about $20.
Poking a wire is free, just use a strand from a 12- or 14-gauge stranded wire.
Spray cleaner is only a couple bucks. Compressed air in cans is about the same.
Full set of o-rings is unfortunately not available from cycleorings.com, but they do carry the intake o-rings.
Bench sync has been covered many times before, here is one listing in the archives.
If you don't have a set of gauges, you will need help with the vacuum sync.
Pre-set the mixture screws to turns out from lightly seated. Warm the engine, tweak each screw for highest rpm.


.

[snark]

Five minutes is a little long. Mine usually is about 2.

Check your idle speed and, make sure your at about 1100RPM. My fast idle is about 4000RPM. Also, did you put in a new set of plugs? They can make a big difference.

[Uncle Jetski]

Hey, Mount Laurel!

I have an '82 450 in Moorestown. As I learned, the bike is very sensitive to air. When I got the bike a few months ago, it had the wrong airbox cover, and it would lunge and hesitate, and I couldn't take the choke off. I got the right one, and now it warms up in 2 minutes, and runs smoothly.

[cfcubed]

<snip>. It seams to take 5 minutes before it warms up enough to ride it. Once fully warmed up it runs very well. Decent power although a little hesitation off idle until your up over 2,000 rpm. Is this typical, the long warm up? <snip>

For a few weeks immediately after my carb rebuild, my 81 450 only needed about 2 mins warm up & off I went...
Then, the very day I went riding w/a guy & bragging about my quick warmup was the *last* day of quick warmups for me....
Since then, gotta wait 5 mins before taking off (just get gear on during that time). I bet some little something is somewhere in the carb(s).
I hesitated to put an inline filter & I guess I should have...

[morrowd]

Check the timing. That solved my slow warm up problem.