GR650 Tempter help needed

[Guest]

Looking for help/opinions before I start to take a look inside the clutch of this bike. Excuse me for a long post but this is going to take some explaining.

Some background. The GR650 Tempter is a parallel twin sold in America for one year, 1983, but sold in Europe for about 10 years. I bought this late last fall as a project and to have to run back and forth to work with. It is completely stock and in great shape...no major rust and everything is all there, but it had straight pipes for exhausts. The PO said it had a "small ticking" sound from the top of the engine. Based on how good this bike looked, it's never been laid down, and guessing the small ticking was caused by needing a valve adjustment...I took the chance. $400.

I have since done the following: 1) adjusted and set the valves which were way off and lead me to believe this was the ticking sound, and installed a new valve cover gasket 2) changed the oil, filter and oil pan gasket. Oil was absolutely clear with nothing in the pan. 3) rebuilt the front forks 4) completely cleaned and rebuilt the carbs. 4) installed a new air filter 5) put on a stock exhaust with new exhaust gaskets

The bike fired right up the first try..great! Everything sounded just fine. No ticking sound...it all seemed good. HOWEVER...took it down the street and at about 3,000 rpms the bike just quit going up in speed and rpms. It felt like it just hit a plateau and wouldn't go any higher in speed or rpms. At this point, a knocking sound started from the left side of the engine. Turned it off. Checked the compression on both cylinders and they read almost exactly the same...130 and 132. So I don't believe it's bad pistons.

Now, this bike comes with a Suzuki "exclusive" feature, according to the manual. It reads like this..."This bike comes with a variable mass device. At low rpm, the centrifugal clutch engages the auxiliary mass so it rotates with the crank. Above approx. 3,000 rpms the extra mass is unnecessary and undesirable so the centrifugal clutch disengages the auxiliary mass."

In plain English, there is an approx. 8 lbs of weight that's attached to the crank for extra power and at 3,000 rpms it releases for better acceleration. It looks something like drum brakes with springs,...

Hopefully I have explained this correctly but if anyone can get to a manual, it's explained on page 1-9. Since my problem happens right about 3,000rpms, right when this auxiliary clutch should disengage, I'm guessing that a spring on this auxiliary mass clutch weight has broken or something invloving this system needs attention.

I'm just looking for any opinions, help, or experience with this "auxiliary clutch" system that might back up my best guess before I go looking. Thanks..

 

[Nessism]

How do you access the weights? If it's possible to see them without splitting the cases I'd have a look.

 

[Guest]

According to the manual, the weight system is behind the stator. So I'll be opening the left side...and taking lots of pics as I go.

 

[oldrookie]

No help, Super, but very interested in what you find.

Old-skool has been inside his GR, but not sure he messed with the flywheel. Hopefully he'll chip in.

 

[oldrookie]

Might also try getting ahold of Big Rich. He has two or three GR's and has done extensive work on them.

He posts mostly in Do The Ton, but it might be worth registering there to get in touch with him.

 

[Guest]

Its like our one way clutch's in a way. But this one has the release for the starter similar to a Bendix drive on an automotive starter.

See here:
http://www.cmsnl.com/suzuki-gr650-x-tempter-1983-usa_model15987/partslist/94158.html#results

The flywheel is just behind the starter gear on the crank shaft and is always engaged by springs pulling on friction blocks that connect the crank start gear to the mass. Once up to speed the centrifugal force pulls the blocks away from the mass and allows the crank to freewheel at higher than 3000 rpm.

If your concerned with the springs I would think it would only disengage the mass early on or if it was stuck engaged it would rev slower than normal.


I have a feeling its not that but that knock could be a few things.
This is all just speculation until you get a stethoscope and find the exact point of the knock. If its the under the stator cover, pull it off and take a look. Something could be rubbing.

What does it do when its not under load ?
Is the oil overfull?
what did the plugs look like ?
Did it bogg as you gave it more gas or backfire or cut out...?
Did it feel like it was running on one cylinder?

 

[Guest]

Thanks oldrookie. I believe my son knows him on Do The Ton. I'll have him ask but I was hoping for some feedback/info here. I hope you got your Tempter sorted out.

 

[Guest]

Thanks Mekanix. I am thinking along the lines that something's come loose and gets stuck when it disengages thereby not allowing it to get past 3,000rpms. And then it starts making noise. It just seems too coincidental that it has this issue right when it's supposed to disengage. I just can't think of what else it could be.

It is located just behind the stator so I'm going to drain the oil before I open it up.

 

[Guest]

What does it feel like when it hits the wall ?

Is the engine under load and struggling or does it just bogg?
I'm guessing you weren't there long enough to tell.

Maybe one of the weights are loose it might be hitting the flywheel as it spins down and the crank speeds up or one of the bolts that hold it all together has backed out and is hitting the flywheel the same way.



Where can i get a manual online for it ?

 

[Guest]

What happens is at about 3000rpms, it just stops going any higher in speed and rpms and stays there. It did the same thing through 4 gears...I didn't want to try it in 5th gear.

I found a manual online a while back but don't recall just where. I purchased a manual about 5 months ago. You might be able to find it online. If not, I guess I could email you the one I downloaded.

 

[oldrookie]

http://gr650.messageboard.nl/forum/viewtopic.php?t=831

What does it feel like when it hits the wall ?

Is the engine under load and struggling or does it just bogg?
I'm guessing you weren't there long enough to tell.

Maybe one of the weights are loose it might be hitting the flywheel as it spins down and the crank speeds up or one of the bolts that hold it all together has backed out and is hitting the flywheel the same way.



Where can i get a manual online for it ?

 

[Guest]

Thanks, Got it .

looking into it.

What happens is at about 3000rpms, it just stops going any higher in speed and rpms and stays there

What happens when you give it more gas? Does it struggle or does it bog.

What happens if you free rev it past 3000?

 

[Guest]

Mechanix...I never really free revved it past 3,000. When it first fired up, I just blipped the throttle and wasn't thinking about revving it high. At that point, I hadn't ridden it.

As for riding it, at about 3000rpms, as you feel yourself getting pushed back in the seat as it goes up in speed, it all of a sudden just stops gaining speed and it feels as if you've hit a wall. The engine continues running. And at that point, the knocking starts. It doesn't knock when you first fire it up...it sounds good.

Thanks for any help.

 

[Guest]

Ok, in that case I'm leaning towards something else causing the problem and guessing carb related.

What does it have for main jets ?
Since it had open pipes I'm guessing the PO jetted it rich just to get it to run.

maybe something is causing it to run really lean at that rpm.

Does it keep knocking after you slow down or is it only when you where at 3000?

Those carbs are very sensitive to air filters and exhaust. The symptoms make it sound like others who have installed pod filters and find their bike doesn't rev past a certain point from running too lean.

 

[Guest]

The carbs were completely cleaned and rebuilt by me so I know that they're good and correct. I believe the PO just wanted to make some noise with the straight pipes.

He also used wood screws to bolt the tank down, drilled out the bolt openings in the instrument cluster so he could use wood screws there too and a few other questionable "fixes".

The knocking does continue after I slowed down and brought her to a stop...just not as much as when the bike was running down the street.

 

[Guest]

I'm still going through the manual to see if anything comes to mind.

There is only a few things that cause an engine to just stop revving like that.

running lean
running rich
cam timing
retarded ignition
tight valves
inoperative vacuum slides

Thats all I can think of.

I can't think of anything mechanical that would cause that.

What does it look like under the cover?

 

[Guest]

Thanks for all your efforts Mechanix. Valves were done and in specs. I just can't understand why she runs just fine until about 3000 rpms. And the knocking doesn't start till then too.

I'm just going to pull that left side case off and take a look just to satisfy my curiosity, as well as being able to eliminate my guessing that it's the auxiliary clutch weight system. Possibly tomorrow if nothing comes up.

Thanks again and I will post what I find in there.

 

[Guest]

Hey, what about an air leak? That would make it run good up to a certain point and run flat like what your getting.

Do you have the auxiliary intake lines hooked up from the bottom of the carb to the intakes?

 

[old_skool]

Sorry, just reading this, I never tore into or behind the stator, so no help here, and as far as a manual goes, I see you have one now, but I posted one in the Tempter thread I started, I asked for it to be added to the manuals, but that's up to BassCliff if he wants it on his site and up to the moderator to add it to the manual sticky, no-one offered to do either after I requested, so either they didn't see it or decided against. Here it is again in case it's different.

http://www.4shared.com/office/uhx2-k-B/Suzuki_GR650X_Service_Manual.html?refurl=d1url

 

[Guest]

Mechanix...yep, the auxiliary air lines from the carbs are hooked up. We're good there. Thanks again.

Old skool, thanks for the input. I actually did go to Basscliff's site to see if he added the manual you offered and saw it wasn't there. And I have been following your Tempter thread. It looks exactly like mine...but your's runs!! And you did a great job on it too. Sorry to hear of your wife's health issues and wish her and you the best. Hang on to the Tempter for now...who knows what might happen. And it looks cool!!

Again, thanks to everyone who's added their thoughts to this thread. It's just time for me to do something new, dig into it and see what I find out.