Technical Question About Carbs for 650GLD - Carb Gurus Needed

[Guest]

Even though the VIN has a manufacture date of 9/82, the bike is titled as 83. Why is that important: because I ordered a Dynojet kit that was good up to 82 650's thinking that it would apply to an 83 without problems. Well, in looking closer at my VIN I see that my model is a GLD which when looking at this table: http://gsarchive.bwringer.com/bikecl...at_height.html you can see that mine was the only model blessed with a different carb set up - regular easy differences like a different main jet and pilot jet, but also stuff that is a little more worrisome to me such as the needle jet size and bypass sizes. The DJ kit swaps out the needle, main jet, and constricts the main air jet with a restrictor plug, so I think I'm okay there, but all the other 650 models have a Y-7 jet and mine has an X-2. Should I be looking for Y-7 needle jets to install (if they even exist)? Is it significant enough to worry about? Or should I invest in non-GLD carbs so that I can start with the correct carb platform? Are the bypass sizes (0.8;0.8;0.8 vs, 0.8;0.7;0.8) and starter jet size a concern also?

Recall that I have a bike that is running pods and 4:1 that runs well when warm, but has fuel issues prior to that point. In not knowing what the PO has done, I'd rather wipe the slate clean and rebuild/modify accordingly - thus my ordering of the DJ kit. The pods are K&Ns.

Thanks in advance.

Geoff

[Steve]

I have never really noticed the differences in the '83 650 carbs.

I looked in my chart and found a few other differences, not sure which ones will matter, or how much.

Specs listed are for '82 / '82 models:
Main jet: 110 / 107.5
Pilot jet: 42.5 / 47.5
Jet needle: 5c45 / 5d59-3
Needle jet: y-7 / x-2
Main air jet: 2 / 1.2
Starter jet: 45 / 32.5
Bypass: 0.8, 0.7, 0.8 / 0.8, 0.8, 0.8
Pilot outlet: 0.7 / 1

Here is how I see the differences:
Smaller main jet for better jetting in an EPA-concious society.
Larger pilot jet to allow better low-throttle operation.
Not sure about the needle specs.
Not sure about the needle jet specs.
Smaller main air jet will make a richer main mixture, probably to compensate for smaller main jet.
Smaller starter jet possible due to larger pilot jet.
Bypass differences are too small to notice. They are the "transition" ports that add mixture just above idle.
Pilot outlet allows more mixture at small throttle openings, but controlled by pilot screw.

Bottom line:
You will be changing the main jets and the needles anyway. It might take a bit more fine-tuning with clip positions or shims, but I think you should be fine with your current carbs. Most of the changes to the carbs were to satisfy EPA regulations, I don't think that is much of a concern, in your case.

.

[UKPR1]

Steve,

Thanks for weighing in...and giving me a little gumption to persevere and at least try. I'll start throwing the kit in he carbs and let the group know what happens for posterity. Gotta love the environmentalists back then...I've been witness to some fairly crazy/ingenuous ideas when it came to vehicles and pollution.

Cheers,

Geoff

[tkent02]

Throw it in and see how it runs. Fine tuning will be required anyway.

[UKPR1]

I think that's what I'll do. I was trying to see if spec sheets existed with which to compare the X-2 jet to the Y-7 predecessor jet, to see if there could be some fundamental flaw, but anything that discusses Mikuni jets seems to skip over those two jets!
Oh well...sometimes test and tune is the only way.

Thanks for your reply.

Geoff

[UKPR1]

I just wanted to say that in tearing into the carbs last night, I was pleasantly surprised to find that my needles bore the 5C45 stamp and my mains were 110. I think it's evident that even though my bike is a GLD, that I have a set of non-GLD carbs, so the Dynojet kit that I purchased should have no issues being incorporated into them. Begs the question of how the bike ran so well with cheap pods, a 4 into 1 and stock jetting, but it did run. I'm excited to see how much better it should/may/will run with proper jetting changes and K&N filters.

Thanks for all of your assistance.

Geoff