Hard to start after sitting a few days or when cold

[Summit670]

I have an 87.  Over the last 5 years or so it seems to get progressively harder to start in sub-70 temperatures even if it has sat for just 10 hours.  This year is really noticeable.  Previous years I've noticed the hard cold starting only after the bike has sat for a few weeks.  Also, just the last month, I've had the engine/exhaust backfire on me when trying to start.  Scared the crap out of me and my Labrador one time.

After it warms up a few minutes it runs fine.


I cleaned the carbs about a year ago but the bowls, main, pilot jets were pretty clean.  The bowls had a little gunk and the jets were clean.  I sprayed carb cleaner thru the passages but didn't pay close attention that those were equally clean because I was looking for another problem at the time (solved with Stic Coils and eventual pickup coil replacement).

Do you think my carb choke circuits are clogged a little or the float levels are in need of adjustment?

[gpzrocker]

Definitely carbs, but I would consider a float charger, helped me an amazing amount. On my GPz, I kept thinking I had the carbs clean until I really looked at the ummmmm pilots?, the really small ones. Had to use a really bright light, compressed air and a guitar wire to fix it.

I also at the time stated that the bike was smarter than I, not starting below 40 degrees.

[cmoore]

When was the last time you adjusted the valves?

[GeeBeav]

When was the last time you adjusted the valves?

+1

[Summit670]

Valves were adjusted 5,000 miles ago.  The hard starting has been going on for many valve adjustments and the backfire deal just began the last few months.

[gpzrocker]

My valves were ok on the GPz and did the same thing too, albeit under 40 degrees. Another thing to look @ is a compression check. IIRC I was low on one cylinder before I did the head gasket and never checked after, didn't ride the bike in the cold any more either. I do think that a compression check will eliminate a lot if nothing else.

Digging back in the memory banks: I think I used to cover the intake on the airbox and it would start better, which made me consider the compression check? Kind of foggy there, although I do remember covering the intake to get it running once or twice.

[Steve in Sunny Fla]

Covering the intake makes it richer, which is what's needed when it's cold. The enrichener jet can indeed get clogged up. They're just slightly larger than the pilot jets. ethanols' evaporation rate is very high, and it will cause a lowering of the fuel level when the bike sits. Putting the petcock on prime for a minute or so prior to attempting to start will help that, but be sure to return it to RUN or you risk getting a hydrolock when you shut down. HTH, Steve

[Summit670]

As a general rule I don't run ethanol unless I'm on a trip and can burn thru the tank of fuel the same day or the next day.

I probably need to pull my carbs this winter and do a more thorough job of cleaning the little passages.   

I replaced the airbox boots about 18 months ago when I had the carbs off.

Will replacing the manifold boots make it a lot easier to install the carbs or are they so short it really doesn't make much difference?

[Steve in Sunny Fla]

really, as long as the airbox boots are soft you're good to go. a little heat from a heat gun softens the fronts if they're on the stiff side - steve