GS300, pipes/pods/jets/issues

[Ric]

So I've had this setup on the bike for awhile now, with .064" spacers on the needles and #127.5 main jets. Still on stock 17.5 pilots, but I pulled the cover plugs and adjusted the pilot screws to as good an idle as can be expected. Spark plugs are fairly new, and have not shown a lean condition anywhere in the throttle.

Issue #1: I know 28?F is a bit cold to ride, but it's my only way to work for now. I'm fine with that - but the bike's right cylinder won't fire on a cold start. I have to choke it(hits on both cylinders), but when I unchoke it I have to give it throttle and wait for the right cylinder to come back to life. Carbs are clean - is this a spark plug issue? Or a pilot screw needing tweaked?

Issue #2: The bike runs fine at light throttle. No herky-jerky, just butter smooth transition all the way to WOT. BUT, dropping from WOT down to light throttle, both cylinders drop out totally, then come back after a half second or so. Do I need to step to a 20 pilot jet?

All in all, the pod conversion has been nothing like the headache I thought it'd be, and I owe it all to the wealth of information on here. Thanks so much!

[Ric]

I should also add that it has zero issues with fuel starvation. I've ran WOT for as long as anyone would want to, and not the first sputter. Floats are set around 21mm.

[trippivot]

pilot is lean. needle is rich

the very FIRST thing you do is richen the pilot jet / slow jet when you go to pods! The biggest question is, does your engine want 1 size larger or 2 sizes larger? - sounds like you need heat energy or more gas to make the leaner cylinder fire...good observation.

Now that it is cold your engine is DEMANDING more gas. before it got cold you probably needed the pilot jet adjustment but the excessive needle shim height masked the problem.

boost your pilot to a 20 don't be surprised if a 22.5 works great. and it sounds like you can handle the after effect of getting your cold start issue resolved.

[Ric]

Aiight, thanks for the help! So 22.5s would be better, you say?

Thinking of doing a step hotter plugs, too. Might help keep the heat where it needs to be?

[trippivot]

I only go 1 step at a time with pilots - so install 20 first - and adjust with the plugs you have now so- if your bike is that predictable it will be easier - to tell difference in jetting and difference in running temperature. - cold start , warm up and how hot it is when you get to work, got a laser pyrometer?

am I correct thinking you have a ngk b8 installed ? 8 is kind of a do it all heat range -- your location is not listed. with aircooled engines hell yes go hotter with the plug when it goes colder than 50 F (B7) - don't be shy to go colder in the summer over 80 (B9) - but the heat range is separate tuning detail than jetting - quicker your engine gets up to temp the less sludge it will produce - and steam off condensation inside the cases - which is very good . you want that sucker to pop up to 180~200F as fast as possible and level off. I'm talking about the head casting - the actual oil temp will be 60 or 80 degrees cooler.

let's not confuse things until you get it jetted a little better -- winter tuning , summer tuning . all while you are trying to keep the same operating temperature .

the cold start and pre-warm up with a cold plug when it's around 70 will make you self doubt your jetting - until engine comes up to temperature. it's tricky to describe but with a predictable machine you'll be able to see what I mean just by swapping plugs one morning and try the other ones the next - you'll see . and when you get that V-max Whoo - hoo - XVZ power /// you wont do a thing with spark plugs because it has a radiator and thermostat.

[Ric]

I'm afraid I haven't got a laser pyrometer. Dad had one, was super handy - why I never thought of getting another one is beyond me, thanks for the reminder!

Locationwise, I'm in Gatlinburg TN, next to the Smoky Mtns. Doesn't get as cold in the winter as up there where yall are, but we do have four seasons. I've definitely scratched my head over the idea of winter jetting vs summer jetting. And I believe you're right about the 8s, too. I'm a hot rod gearhead, so I know how the plug's heat range plays in them. Just haven't toyed with the notion in bikes much - I'd assume it's a more profound effect in air-cooled engines.

And yep... that Vmax will be nice. Even nicer if I can do it up like I hope to - bore/stroke it to 1688cc, cam it, Venture gearset, chain drive, and a back wheel that takes RADIALS. A good 200 hp of reliability. B(

[Ric]

Well? I have 20s and 22.5s on the way, along with a pair of 130 main jets because it seems to go flat in colder temps at WOT(Probably should've went with 130s anyway - I'm at 1300 ft elevation and thought I could try a size leaner). I have a pair of D7EA spark plugs to put in soon as this warm spell passes through.

Couple of touch-ups with the exhaust, A 39-tooth back sprocket, and I think this bike will be done... at least till I figure out how to raise compression to about 10:1, ceramic coat the header pipes/cylinders/combustion chambers/exhaust runners/piston tops, install gapless rings, a 250 6-speed gearset, disc brake conversion, tachometer.... :P

[Ric]

#20 pilots and #130 mains are in. She fired right up, didn't have to wait for the right cylinder to wake up! We'll see how she does on the way to work in the morning.

I did strip out the threads on the one corner where the throttle bracket screws on. Fixed it with a longer bolt and a nut on the bottom. B(

[Ric]

Well? Light throttle is impressive! Especially for a 300! WOT is equally as impressive with the 130s. In between, it's still got issues. More so now than before. On the way up the last hill home, I think I heard detonation and I lost the right cylinder for a bit. Does that sound like what an overly rich engine does? I'm going to drop the needles back in the jets a little and see what that does. Sound right?

[Ric]

Going to Home Depot(because THAT'S where to find old motorcycle parts) to hunt down some spacers.

Flash forward twenty minutes....

Got two 4-packs of stainless 2.5mm flat washers. Four of them stack up to roughly the same height as the OEM nylon spacer. So I'm gonna stick three on each needle and see what she does.

Thinking I should've done this the first time. The fiber washers are more precise, but I kinda think the gasoline has dissolved them and made the midrange throttle stupid rich.

[Ric]

Well? Just got everything back together. Turns out, I only put one of those fiber washers on each needle, and at .032" each, she was likely dumping way too much gas in at upper-mid throttle. Plugs showed it too... left one was beyond black, and right one had raw gas on it. So I left the one fiber washer in, and added two of the aforementioned stainless washers to each needle. She starts without choke, and both cylinders come right to life! We'll see how riding goes - after the monsoon passes.

[Ric]

20151228_081932.jpg
Here's the left float level, for those curious.

[Ric]

20151228_074537.jpg

And the right float level.

[hjacobmiller]

Any updates?