• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

crankshaft question (really wierd)

  • Thread starter Thread starter sambo
  • Start date Start date
S

sambo

Guest
I bought a 1978 GS1000 engine from a guy here on the GSR, I did a top end rebuild and got the engine to run, but I've been having trouble with the far left cylinder (relative to the bike). I checked my compression and it was low on that cylinder, then I took the valve cover off and checked to make sure I could spin the buckets, i could. While I was doing this and turning the engine over by hand I noticed the the two center pistons moved up and down together perfectly, but the two outer pistons didn't. the piston on the far left was slightly behind the piston on the far right.

This doesn't seem right to me because when all the other pistons are at TDC the cam lobes for that piston are pretty much horizontal and pointing exactly away from eachother, but when the piston on the far left is at TDC the lobes are different.

Is it possible that my crankshaft could have shifted, causing that piston to be in different spot relative to the others? I hear about people welding there crankshafts for high performance engines is this what they are trying to prevent?

Thanks in advance, Sam
 
Sounds like the motor has a twisted crank. Not sure where you are located but I have a 1000 motor that I could get rid of. TH
 
I'm located in New Jersey. So a twisted crank is a common problem?
 
If my memory serves me correctly, cranks twisted on this model on a regular basis. Later models had the crank pins welded to prevent this. You may be able to find someone to re-align, balance and weld that puppy.

The general thinking back then was that this issue happened on sudden de-acceleration of the crank mass.
 
The 78s did have that crank slippage problem. Later ones used something like Locktite to cure it.
The common repair is to spot weld the pins in place. Someplace like APE can probably realign and weld it for you.
 
Thanks for all your help, so the outside pistons are supossed to go up up and down simultaneously. I guess I'm pulling the whole engine apart.
 
check out Orient Express in Freeport New York. They are a high performance shop that specializes in this type of problem, and are a lot closer to you than falicon or ape
 
sambo said:
Thanks for all your help, so the outside pistons are supossed to go up up and down simultaneously. I guess I'm pulling the whole engine apart.
Click to expand...

I thought I was running into problems. Good luck and enjoy.
 
Sam, yes the two outside pistons 1 & 4 should be in sync with each other just like 2 & 3. Yes, the motor will have to come back apart. I have a motor with a good crank that needs a home but I'm down South. Todd Horton
 
Do a need special tools/a lot of experience to align the crank and weld it? I'm a decent welder, but don't really know how I would go about un-twisting the crank?
 
Sam, The crank has to be pressed apart. I think that they use a special ground rod inserted in the rod end bores to align it and it's pressed back together and welded. TH
 
I guess I better have it done, I contacted Orient express and they told me to go to Falicon, so that sounds like the plan. Thanks, for everyones help, I love the GSR!
 
Sam, good luck with Falicon, they don't like to do small jobs anymore. Every crank I have sent to them needed the rods replaced according to them. TH
 
sambo said:
I bought a 1978 GS1000 engine from a guy here on the GSR, I did a top end rebuild and got the engine to run, but I've been having trouble with the far left cylinder (relative to the bike). I checked my compression and it was low on that cylinder, then I took the valve cover off and checked to make sure I could spin the buckets, i could. While I was doing this and turning the engine over by hand I noticed the the two center pistons moved up and down together perfectly, but the two outer pistons didn't. the piston on the far left was slightly behind the piston on the far right.

This doesn't seem right to me because when all the other pistons are at TDC the cam lobes for that piston are pretty much horizontal and pointing exactly away from eachother, but when the piston on the far left is at TDC the lobes are different.

Is it possible that my crankshaft could have shifted, causing that piston to be in different spot relative to the others? I hear about people welding there crankshafts for high performance engines is this what they are trying to prevent?

Thanks in advance, Sam
Click to expand...

You are describing a crank that is possibly "out of phase". It does happen. Sometimes from the engine "hydrolocking" from raw fuel that weeped into the cylinder, sometimes a sparkplug chunk drops into the cylinder and so on. The only to check for a correctly phased crank is with a precision travel indicator.
 
Yep! I did the same thing on my GS1000 when I was 19, I was racing a Honda NSX (car) and my motor went BANG!!!
I rebuilt the engine, 4 pistons and 4 valves.... cost me a small fortune and it would not run right.....
Stripped it completely down and the crank was twisted!!!!
Don't fool with that crank, GET ANOTHER ONE......
 
Do I have to get another 78 crank or would another year fit. I'm just wondering because I've heard 78s were the only ones that had a real problem with this, and I would hate to have to do this again. Although, I'm getting pretty good at tearing my engine down.
 
I'm not sure, Post the question, I'm sure someone will know, maybe Keith Krause.....
 
Give John Pierson a call. He is THE crank guy I use. He is in Dayton Ohio. He can help. He has done every GS crank I have had built and never a problem. He is very reasonable also.
937-839-9723. Terry.
 
You must log in or register to reply here.
Back
Top