Low Idle/Stalling when HOT

[Nessism]

Compression is 120 across all four, I've put in new rings so I rechecked the ring end gaps yesterday when in the cylinders and they are between .3mm and .2mm.

It used to have points with the mechanical advance but now has a Dyna S. I checked the timing and it was timed to the first mark (with timing light attached to #4 plug wire, not static), not the advanced mark, so I corrected that. It also has Dyna Green coils. When it's showing this symptom, there's at least 12.5v measured at the coil input. (Coil relay mod and a Honda regulator with the sense wire attached to the coil relay trigger wire and a new AGM battery) All of the valve's lashes (sp?) are at the high end between .06 and .09.

It runs great when it's not smoking hot. It's completely smooth across the entire powerband. No throttle inputs hesitate, surge or pop. Cruising is smooth. I'm really happy with it except for when it gets hot and stopped at a light. When it's rolling again, everything is fine.

I can't get past the fact that the ventilation hose has started to melt. It really shouldn't be doing that. At what temp is it considered overheating?

Thanks for all the help,

Rob

Hi Rob,

As long as there is airflow over the engine it should be fine. Never run an aircooled bike in your driveway for extended periods of time without a fan blowing on the engine. Synthetic oil is recommended for hot temp riding since it doesn't thin out as bad as dino oil. Rotella synthetic is good stuff and fairly reasonable in price. The OE Suzuki vent tube is quite expensive but made from good material that won't melt. Is yours the original or did someone install an aftermarket piece?

I'm confused about this business with the ring gap. How can you check the ring gap on an engine that's assembled? Did you tear down the engine again? Please explain.

I'm also confused about the reference to the points. The '80 GS550's came with electronic ignition so no points. What year is that bike again?

If you actually have an older 550 with VM carbs the symptom you describe sounds like a rich mixture. My old 550 did as you say and I fixed it by turning in the VM pilot fuel screw to 3/4 of a turn open from lightly seated.

Good luck

[ChicagoRob]

Hi Rob,

As long as there is airflow over the engine it should be fine. Never run an aircooled bike in your driveway for extended periods of time without a fan blowing on the engine. Synthetic oil is recommended for hot temp riding since it doesn't thin out as bad as dino oil. Rotella synthetic is good stuff and fairly reasonable in price. The OE Suzuki vent tube is quite expensive but made from good material that won't melt. Is yours the original or did someone install an aftermarket piece?

I'm confused about this business with the ring gap. How can you check the ring gap on an engine that's assembled? Did you tear down the engine again? Please explain.

I'm also confused about the reference to the points. The '80 GS550's came with electronic ignition so no points. What year is that bike again?

If you actually have an older 550 with VM carbs the symptom you describe sounds like a rich mixture. My old 550 did as you say and I fixed it by turning in the VM pilot fuel screw to 3/4 of a turn open from lightly seated.

Good luck

Thanks Ed.

It's the stock vent tube and yes, it's a bit pricey. I'm running regular 10-40w in it now. I'll switch over.

Yes, I tore down the engine and removed the barrels and the rings from the pistons and then followed the procedure in the Clymer manual. That is what I meant when I said that I checked them in the barrels. The barrels were off and the rings were out and pushed down into the cylinder 1 inch. It wasn't a big deal. A few hours start to finish. When I put it together, there were a few gaps that were at .1 and I figured that maybe they'd be getting too tight so I found them and turned them into .3mm's. I'm really grasping at straws, aren't I?

You sure do know your bikes. Yes, this one came with the factory electronic points and ignitor box. This was the changeover year. The PO had installed a mechanical advance unit and the Dyna S. It's wired to bypass the ignitor box. As far as I can tell, this is all per Dyna's instructions. But Dyna also says to time it to the advance mark and this one was not. Maybe I can't trust the mark on the replaced advance unit, but I figured that I should follow Dyna's instructions to the letter. I had the problem before I adjusted the timing and I was hoping that this would fix it. It did not. Here's a link to the instructions: http://www.dynaonline.com/skins/down.../DS3-1_3-2.pdf

It has CV carbs that are bone stock (I checked the size of every internal yesterday as well) The air screws are at 3.5 turns. Three of the plugs are showing just slightly rich but #4 is still too rich. I'm setting the float height down a bit on that one.

Maybe it's just because my test runs are too strenuous. I'm going try to give it just a normal cruise (to WalMart I guess to get some synthetic oil) and see what happens.

Thanks again for the help.

Rob

[Nessism]

So when you set the timing did you hold the advancer against the spring to full advance and then align to the TF mark?

As far as stripping down the engine goes, that's fine as long as you replace the head gasket each time. Not sure if I'm understand correctly but I hope you used a bottle brush hone in the cylinders before you installed the rings that first time too.

[ChicagoRob]

So when you set the timing did you hold the advancer against the spring to full advance and then align to the TF mark?

As far as stripping down the engine goes, that's fine as long as you replace the head gasket each time. Not sure if I'm understand correctly but I hope you used a bottle brush hone in the cylinders before you installed the rings that first time too.

No, I did not. The Dyna plate covers all of that (except for a peep hole) so there is no way for me to manipulate the advance when it's running. I did check that the weights were present and that it moved freely. To the right of the TF mark there is the A mark. I timed to that by strobe at 2.5k rpm. It was exactly as Dyna described in the install instructions.

Here's a pick from an ebay auction. (Sorry, I don't have one of my own.) At about 5 oclock on the advance mechanism you can see the TF mark. At about 6 oclock the A mark. The advance mechanism is needed for the Dyna S because that's what it's magnet attaches to.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?VISuperSize&item=250707463066

Yes, new head gasket. Someone in your neck of the woods (well, California) is ebay'ing superceeded OEM ones for $25 delivered. $10 for the base gasket. There are no apparent leaks.

I took the cylinders and head to a machine shop before I assembled for the first time. They machined the mating surfaces, honed the cylinders and said that the cylinders were in mint condition. Besides the mating surface, they didn't do anything else to the head.