Topic: Running a hotter plug to lean out the mix?

[SpAmSoNiTe]

Hi all,

After several months of fighting with my 650 last fall/this spring, it FINALLY stopped overflowing from the #4 carb on it's own and I've finally gotten to ride it this summer.  Only problem now is, she'll barely make it up to highway speeds, and it's worse when it's hotter outside(yesterday went for a ride when it was 90 deg., and she struggled to hit 65).  I think I've pretty much determined it's running too rich(with the carb faq and a plug chop; plugs are sooty and insulator is medium brown-ish).  I know that you can run colder heat range plugs to enrichen a mixture, but can you run slightly hotter ones to slightly lean it out?

I've taken off the air filter cover and held the air filter on with just screws and washers(it would barely hit 60 before that), but don't want to completely remove the filter.. I'm actually nervous about removing the bowls to change out the mains until winter because I'm afraid she'll start overflowing again and I'll lose the end of the summer to ride(silly, but I fought with that stupid carb for over six months before it quit leaking on it's own!)

      Thanks,
                Sam.

[MCRider]

Hi all,

After several months of fighting with my 650 last fall/this spring, it FINALLY stopped overflowing from the #4 carb on it's own and I've finally gotten to ride it this summer.  Only problem now is, she'll barely make it up to highway speeds, and it's worse when it's hotter outside(yesterday went for a ride when it was 90 deg., and she struggled to hit 65).  I think I've pretty much determined it's running too rich(with the carb faq and a plug chop; plugs are sooty and insulator is medium brown-ish).  I know that you can run colder heat range plugs to enrichen a mixture, but can you run slightly hotter ones to slightly lean it out?

I've taken off the air filter cover and held the air filter on with just screws and washers(it would barely hit 60 before that), but don't want to completely remove the filter.. I'm actually nervous about removing the bowls to change out the mains until winter because I'm afraid she'll start overflowing again and I'll lose the end of the summer to ride(silly, but I fought with that stupid carb for over six months before it quit leaking on it's own!)

      Thanks,
                Sam.

I'm not an expert on this issue, or others for that matter, but I'll throw this out. Running a hotter plug won't lean out the mixture. It may allow a too rich mixture to fire, but its a bandaid over a problem which still exists. Too rich.

[KeithB]

I know that you can run colder heat range plugs to enrichen a mixture, but can you run slightly hotter ones to slightly lean it out?

The plug temp doesn't affect the mixture. That's a carb thing.
What a hotter plug can do is help prevent fouling if, say, you run around town a lot rather than highway riding if you have a slightly rich mixture.
I did go to a hotter plug on the '72 and found it worked well at keeping the plug clean but I don't do long highway rides.
On the '78, stock plugs were fine.
If you are having problems hitting 60MPH, I would suggest a more comprehensive trouble shooting session is required.
Sort the problem out before changing plugs from stock temp range.
Make sure the jets are clean...clean...clean , check float level and confirm correct timing. Also check that the correct main jet is installed.
I'm sure others here will have some more suggestions.
Once you find and correct the problem, get new plugs too.
Let us know how you make out.

[TwoTired]

Check the head pipe temps for even heat.  A 4 running on 3 "under-performs".

[Duke McDukiedook]

Check for spark/fuel, check your float levels. Remove carbs and clean them thoroughly, paying specific attention to the idle/pilot circuit.

[Kframe]

Hi all,

After several months of fighting with my 650 last fall/this spring, it FINALLY stopped overflowing from the #4 carb on it's own .....  Only problem now is, she'll barely make it up to highway speeds....

Check the head pipe temps for even heat.  A 4 running on 3 "under-performs".

If the carb stopped overflowing on its own, maybe the float is stuck shut instead of open (which was causing your flooding).

Through forum help and methodical troubleshooting I found out today that this was my issue. 
It's certainly worth a look!

Start the bike from cold, take a wet paper towel and touch it to each header just past the top bend, within a minute of running all should steam and sizzle vigorously. 
-K

[SpAmSoNiTe]

Got good spark at all of them, #4 seems to idle a little cooler than the others(this was the one overflowing), and everything SHOULD be  as sparkling as can be with the number of times I tore down/cleaned them over the whole overflow debacle. I gotta say that whom ever decided that a pressed in jet was a smart idea really ought to be shot   Float heights are permanently set by the plastic floats..  Guess I'll probably just have to suck it up and pull the bowls and check to make sure the main sizes are actually correct(I just cleaned 'em.. never checked their size)...

Hi all,

After several months of fighting with my 650 last fall/this spring, it FINALLY stopped overflowing from the #4 carb on it's own .....  Only problem now is, she'll barely make it up to highway speeds....

Check the head pipe temps for even heat.  A 4 running on 3 "under-performs".

If the carb stopped overflowing on its own, maybe the float is stuck shut instead of open (which was causing your flooding).

Through forum help and methodical troubleshooting I found out today that this was my issue. 
It's certainly worth a look!

Start the bike from cold, take a wet paper towel and touch it to each header just past the top bend, within a minute of running all should steam and sizzle vigorously. 
-K

[TwoTired]

Got good spark at all of them, #4 seems to idle a little cooler than the others(this was the one overflowing), and everything SHOULD be  as sparkling as can be with the number of times I tore down/cleaned them over the whole overflow debacle. I gotta say that whom ever decided that a pressed in jet was a smart idea really ought to be shot  

That would be the EPA's influence on import requirements.

#4 cool at idle is likely a pilot jet issue.  The same crud that makes the bowl overflow, blocks tiny jets, too.

Check you tank for rust/debris and gas filter, too.  Feed clean carbs dirt and they aren't clean any longer.

Cheers,

[Duke McDukiedook]

Float height is adjusted by bending the metal tang on the float up or down, also check to make sure you did not put that float in upside down.