GS650 idles but dies with throttle

[Steve]

Hi, I have a Real Gasket. ... I feel I need to use it cuz its 30 bucks. ...

You feel that you have to use it because it set you back a bit?

On your 1000, it's not so bad, but on powderhound's 650, it's a definite No-No. On the 650, the tach drive is in the valve cover, not the head, so the thick gasket prevents the driven gear from meshing properly with the drive gear.

.

[powderhound]

Alright, just got through doing the first round of the valve shim shuffle. Looks like I must have been simply mistaken when I was taking measurements before. After running through them, again, I had a 2.65x shim where I had thought it was a 2.70. It looks like I was able to get pretty close to within spec (not including shooting to be on the looser side of the range). As soon as I hit submit I'm going to be placing an order with Z1.

	Cylinder 1	Cylinder 2	Cylinder 3	Cylinder 4
Orig. exhaust shim	2.65	2.70	2.65	2.65
New exhaust shim	2.60	2.65x	(no change)	(no change)
Final clearance	.063mm	.063mm	.038mm	.038mm
Orig. intake shim	2.60	2.65	2.65	2.65x
New intake shim	2.70 (temp)	(no change)	(no change)	2.65
Final clearance	<.038mm	.051mm	.038mm	.051mm

As per your suggestion @Steve, I'll get both a 2.55 and a 2.50 to make sure I've got options for intake 1. I'll also pick up a few 2.60 shims just in case / for the next time since it looks like the valves will be getting out of spec sooner rather than later.

Also, I'm stubbornly going to stick with the metric system. Feels wrong to work on a Japanese bike using imperial units.

CD

[Steve]

Also, I'm stubbornly going to stick with the metric system. Feels wrong to work on a Japanese bike using imperial units.

CD

Well, then, why not get UNstubborn enough to get some real metric feelers?

Those numbers you are posting are the metric APPROXIMATIONS on the INCH feelers you are using.

No matter, the spreadsheet will handle both systems.

And don't forget to get your new torque wrench that shows newton-meters.

And your tire pressure meter that displays in kilopascals.

.

[powderhound]

Well played, sir!

[powderhound]

Alright, I just finished up my valve adjustment, and they should all be in spec. Intake #1 is slightly loose, but it's significantly better than it was before. However, I'm still having similar issues as before. When I give it ~1/8th throttle, it revs fine, I've taken it up to ~4k rpm and it's about as good as I can tell without it on the road. However, if I give it more throttle than that (e.g. ~1/2 throttle), then the engine falls flat on it's face and dies. I took a quick video to hopefully show what I mean:

I'm still running with a piece of foam for a Briggs and Stratton inside the stock airbox, since my air filter doesn't come in until Friday. I'm seeing a small amount of bluish smoke from the right side exhaust, and it does smell a bit rich.

Things I've done:

• Valve adjustment
• Cleaned carbs
• Adjust fuel mixture screw to ~2.25 turns
• Re-installed stock airbox (but with temporary foam filter)

Next steps:

• Install stock air filter (Friday)
• Vacuum sync carbs
• ???

Anyone have any suggestions for other next steps or things I can test?

Thank you all again for working through this with me!

Carson

[Steve]

Anyone have any suggestions for other next steps or things I can test?

Just for fun and games, turn your mixture screws out to 3 turns.

Also, try turning the throttle just a little bit slower.

These carbs do not have accelerator pumps. The vacuum-operated slide does a fine job in a stock situation, but your airbox and filter is not stock, so you need a bit of extra gas. Until you get everything else resolved, the extra turn on the mixture screws might be enough. It's certainly easy and cheap enough to try and just as easily and cheaply reversible.

.

[powderhound]

Alright, after a couple of weeks of tinkering, the bike still isn't running right. It idles fine at about 1100rpm, and it revs up with throttle (but still dies with throttle quickly applied). However, when it's in gear, the engine dies as soon as any load is put on it. Even slowly accelerating up a small hill (out of the garage) is enough to do it in.

I've now got the stock airbox and a UNI factory replacement filter, and as far as I can tell, everything is pretty well sealed up.

I was hoping to take the bike around the block to see if I could get some more info about how the engine responds under load, 1/4 throttle, 1/2 throttle, etc, but I could barely get out of the driveway, let alone take it for a test drive. I'm starting to think that I might not be getting full compression in the cylinders. Anyone have any advice for tackling this one?

[tom203]

check that your mechanical advancer is free to move. Do your vacuum diaphragms look good with tabs in correct spot?

[BigD_83]

I'm starting to think that I might not be getting full compression in the cylinders. Anyone have any advice for tackling this one?

Have you had a chance to test the compression since you got the bike?

[roeme]

powderhound, what kind of instrument buckets are you using? I'm searching for something like that for months now!

(oh and anybody else who knows.)

[Chancho196]

That sounds like it's really lean. Are you sure the jets are meant for the 650? And float heights are correct?

[powderhound]

roeme: They're actually the stock gauges, with the center electronics removed. It was actually really easy to remove once the gauges were off the bike.

Chancho196: The float heights were correct, but I hadn't verified the jets. It turns out that the bike was having a compression issue. Unfortunately I just didn't have the time / resources to do an engine rebuild, so it's off to a new owner. I'm hoping to save for the winter and then get back into the GS game next summer.