82 650GL breaks up after 5500 RPM

[Guest]

Started this in one of the general forums, however, seeing how things have turned, figured it was more appropriate here....

Bought an 82 650GL early last spring. Originally was going to use it as a parts roach for my 81 650G, but after getting it home decided she was worth keeping. PO said he had put the Pods on it and the 4 into 1 header; also said he rejetted it and rebuilt the carbs (had asked him if he still had the stock exhaust, said he threw it away). On the ride home, it ran great, definitely felt spunkier than the G, so figured he did rejet and rebuild.

Started riding it around a bit, and working out some of the kinks (brakes, some oil leaks, etc). I had a suspicion it was running lean, so I pulled the carbs and checked the O rings behind the intake boots. Yup, original dry and crusty. Replaced them. Took it out for a spin and it absolutely ran like shiat. Stalled on me numerous times, barely got it home. Felt like it was running ubber rich.

I pulled the carbs off and decided to confirm if he really rejetted.....nope, validated they were stock jet sizes. Ordered a set of O rings from Robert Barr, as most looked original. PO did clean the carbs well though - all orifices were clear when i sprayed carb cleaner through them, and they looked clean too.

Also scored a stock air box (both pieces for $40!) and replaced the cheap pods he had on it.

So at this point I have: stock jets, stock airbox, 4 into 1 header. It runs really well up to 5.5k and then it starts to break up really bad (like it won't accelerate any further), if I ease up on the throttle it will pull to about 7k and then start breaking up again. I tried the main mixture screws at 2 turns out and at 3 turns out; seemed to run and idle better at two.

I haven't sync'd the carbs yet (will have to bite the bullet and buy the tool), and yes, need to check and adjust the valves.

After that, what else should I look for? I know it's not going to be perfect with the 4 into 1 header, but it should rev past 5.5k (it did before even with the pods and stock jets).

Thanks,
Mike

[JTGS850GL]

Don't even bother with judging the bike until you've completed the valve adjustment and then sync. These bikes are pretty picky about having those two things completed. The 4 into 1 header may need you to bump the main up one size along with raising the needle.

[Wingsconsin]

maybe worth considering

This may be grasping at straws but this is a classic symptom of a failing stator on a Honda CX500.
It has something to do with the cdi and the stator not being able to supply enough power to run everything at advaced RPMs . Easing it up lessens the demand and allows for higher RPMs.
The CX cure is new stator, cdi box .
The electronic ignition mitigates nuch of this issue ...but maybe you can think about it ...

Or I may be way off...

[tom203]

Definitely check valves-don't wait. While you got cam cover off, doublecheck camshafts to crank timing. Since it ran past 5500 with old pods. I'd rule out the ignition system as the culprit for now. You need to pass alot of air at high rpms- how's the air filter look? make sure the intakes to airfilter box aren't blocked with stuff.

[gustovh]

Check to make sure your cams are timed right, a retarded 1 pin intake cam will give you your symptoms.
V

[mhobryan]

Bit the bullet and ordered the carb sync tool off of flea bay last night. I'm bacheloring it this weekend, so will adjust valves .... maybe I will get lucky and between the 81 and 82 I won't have to order any shims.

No blockages in the box, filter looked okay.

[mhobryan]

This may be grasping at straws but this is a classic symptom of a failing stator on a Honda CX500.
It has something to do with the cdi and the stator not being able to supply enough power to run everything at advaced RPMs . Easing it up lessens the demand and allows for higher RPMs.
The CX cure is new stator, cdi box .
The electronic ignition mitigates nuch of this issue ...but maybe you can think about it ...

Or I may be way off...

You may be on to something here ... I did the 'quick test' and found the battery may be a bit weak, only 12.1 volts w/ key off. Had to throw the battery charger on it to get it started. idle test was okay, but at 2500 rpm at was at 14.5 volts, and at 4000 rpmish it was at 16.3 volts

I did set the main mixture screws and balance the carbs, that made it run smoother under 5.5k, but still breaks up. will adjust valves next and re-balance.

[OldVet66]

And soon it's going to be 0 volts. You need to replace your R/R. 16.3 volts will boil the battery dry, reduce the life of your bulbs and fry your stator, not to mention really overheating any existing tenuous connections in your wiring harness, and probably your ignition. Suzuki uses an electronic ignition on the newer bikes after '80, but I don't believe they used a CDI. You need to inspect the stator, so I would order gaskets now. If the stator is darker than a dark amber where you can still clearly see the individual stator windings, it has already started to degrade the winding insulation and is on it's way to failure. Any blackened bubbling is a sure sign of shorted windings. It can still work for a while if it is just dark and you can't see through the amber coating, mine lasted a year.

[tom203]

As Oldvet66 says, you got charging problems-anything above 15 volts means trouble, be happy that you haven't fried the ignitor (it's not a CDI). The ignitor has no control over the charging system. Might be bad connections, but more likely your R/R has lost its mind.

[mhobryan]

Yeah, after seeing those readings, I figured my R/R was toast... had a hunch it was over charging the battery and this confirmed it. I replaced the gasket last year b/c it was leaking pretty bad - stator looked okay then (haven't put 100 miles on it since then).

Also just checked the valves ... thinnest feeler gauge I have is .0015, and only #2 intake had enough clearance to allow it to pass. Will have to order one thin shim to use as a baseline to find the correct sizes I need on the other 7.

[OldVet66]

Z1 has feeler gauges that cover the two sizes you need to do your valve adjustments. There is one on each end angled perfectly for the job. Being shorter than standard gauges, they are a lot more durable.

[tom203]

You'll likely need a cam cover gasket- make sure you get correct one. Part way into model year 82 they added an additional cover bolt (cam tunnel front opposite tach drive side).
I use .0015 inch as a minimum aiming for high(or more) side of clearance as normal wear reduces it. It's worth getting a cheap micrometer to measure shims as the markings aren't perfect. Once you know what sizes you need, consider joining shim club on here (member ghostgs1) . DO NOT turn engine over with no shim in a bucket!

[mhobryan]

You'll likely need a cam cover gasket- make sure you get correct one. Part way into model year 82 they added an additional cover bolt (cam tunnel front opposite tach drive side).
I use .0015 inch as a minimum aiming for high(or more) side of clearance as normal wear reduces it. It's worth getting a cheap micrometer to measure shims as the markings aren't perfect. Once you know what sizes you need, consider joining shim club on here (member ghostgs1) . DO NOT turn engine over with no shim in a bucket!

Already have the gasket (actually have two, one for the '81 and one for the '82)- ordered it last year in anticipation of doing the valves. Will validate it is the right one.

Do have a question - I dropped a piece of the old gasket down into the cavity containing the timing chain.... my hope is that I can drain the oil and it will come out...wishful thinking?

[JTGS850GL]

That piece of gasket shouldn't be a problem. Yes, drain the oil and see if it comes out, but it shouldn't cause too much of a problem. Most everything gets fed from strained and filtered oil so no gasket will get in there. Everything else will just chew it to pieces small enough to get picked up by the filter in the end.

[mhobryan]

Thanks JT - Kinda what I thought about the gasket.

Could not find any shims locally, so ordered the skinniest available from Z Enterprises (2.30 IIRC) also ordered one each of 2.4 and 2.45 as I was paying $7 for shipping anyways. Should have them by this weekend. Too bad these aren't like my A/C VW bus, or my early 90's BMW (or for that matter the 16V 'Zuki's) with adjustable tappets.