cbfb
3rd December 2010, 18:57
Hey,
You may remember me from such posts as Getting pistons back into cylinders (http://www.kiwibiker.co.nz/forums/showthread.php/131232-Getting-pistons-back-into-cylinders!) and the slightly melodramatic Worst nightmare come true (http://www.kiwibiker.co.nz/forums/showthread.php/131001-Worst-nightmare-come-true...). Yep, I'm the one who's rebuilding the top end of his 250 Bandit. I know I should probably have involved a mechanic a week or two ago but hey I enjoy this stuff and I won't give up now, I think you can do anything if you put your mind to it. Plus financially it's either do it myself or not have a bike.
Well all has been going well, got the head on, checked that the crank rotates ok, no worries there. Put shims and tappets in, then move on to cams:
- Check crank is at TDC
- Insert exhaust cam, aligning timing marks as per GSX250F Service Manual (https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B8ODLPFUxFTpOTY5ZjA4MjgtNjllNi00YWViLWE0Zjc tMDYyNGJkODhlZWJh&hl=en_GB) p3-51
- Take up slack from crank sprocket then engage chain with exhaust cam sprocket.
- Insert intake cam, aligning timing marks as per diagram.
- Engage 16th pin from mark on exhaust cam with mark on intake cam.
- Fit and torque down journal holders, moving diagonally and across holders to make sure cams are bedded down evenly.
- Use screwdriver to wind back cam chain tensioner pushrod.
- Install tensioner, then release pushrod
At this point, the job should be done and the crank should rotate freely. Unfortunately (having attempted this 5 times already) this isn't the case. A few degrees of rotation and everything locks up. There seems to be a lot of slack between the intake and exhaust cams prior to fitting the journal holders which doesn't look right. At first I thought TDC is not right, but have checked with a wooden rod to make sure pistons on #1 and #4 cyls are right up. Have also tried putting intake cam in first instead. What seems to be happening is either:
1. As I'm tightening up the journal holders, the chain jumps back a pin (so there's only 15 pins in the link between sprockets).
2. The chain stays on between tightening, but as soon as I rotate the crank after installing the tensioner, there's a clunk and everything locks up.
I am thinking that it's the chain jamming somewhere (have looked down into the crankcase and can't see anything obvious). Have heard bad things about Suzuki tensioners in general (internet rumours, not sure what they're worth), so maybe that's at fault?
Anyway... if anyone could suggest what to try next I would be VERY grateful. The weather is great and I just want to ride, not be stuck in my stinking hot workshop :(
p.s. Please don't tell me to go to a mechanic, it's something I want to do on my own (with help from the generous folk on KB of course). And yes I know it would probably be wise to leave this to the pros, but I enjoy it so there :p
You may remember me from such posts as Getting pistons back into cylinders (http://www.kiwibiker.co.nz/forums/showthread.php/131232-Getting-pistons-back-into-cylinders!) and the slightly melodramatic Worst nightmare come true (http://www.kiwibiker.co.nz/forums/showthread.php/131001-Worst-nightmare-come-true...). Yep, I'm the one who's rebuilding the top end of his 250 Bandit. I know I should probably have involved a mechanic a week or two ago but hey I enjoy this stuff and I won't give up now, I think you can do anything if you put your mind to it. Plus financially it's either do it myself or not have a bike.
Well all has been going well, got the head on, checked that the crank rotates ok, no worries there. Put shims and tappets in, then move on to cams:
- Check crank is at TDC
- Insert exhaust cam, aligning timing marks as per GSX250F Service Manual (https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B8ODLPFUxFTpOTY5ZjA4MjgtNjllNi00YWViLWE0Zjc tMDYyNGJkODhlZWJh&hl=en_GB) p3-51
- Take up slack from crank sprocket then engage chain with exhaust cam sprocket.
- Insert intake cam, aligning timing marks as per diagram.
- Engage 16th pin from mark on exhaust cam with mark on intake cam.
- Fit and torque down journal holders, moving diagonally and across holders to make sure cams are bedded down evenly.
- Use screwdriver to wind back cam chain tensioner pushrod.
- Install tensioner, then release pushrod
At this point, the job should be done and the crank should rotate freely. Unfortunately (having attempted this 5 times already) this isn't the case. A few degrees of rotation and everything locks up. There seems to be a lot of slack between the intake and exhaust cams prior to fitting the journal holders which doesn't look right. At first I thought TDC is not right, but have checked with a wooden rod to make sure pistons on #1 and #4 cyls are right up. Have also tried putting intake cam in first instead. What seems to be happening is either:
1. As I'm tightening up the journal holders, the chain jumps back a pin (so there's only 15 pins in the link between sprockets).
2. The chain stays on between tightening, but as soon as I rotate the crank after installing the tensioner, there's a clunk and everything locks up.
I am thinking that it's the chain jamming somewhere (have looked down into the crankcase and can't see anything obvious). Have heard bad things about Suzuki tensioners in general (internet rumours, not sure what they're worth), so maybe that's at fault?
Anyway... if anyone could suggest what to try next I would be VERY grateful. The weather is great and I just want to ride, not be stuck in my stinking hot workshop :(
p.s. Please don't tell me to go to a mechanic, it's something I want to do on my own (with help from the generous folk on KB of course). And yes I know it would probably be wise to leave this to the pros, but I enjoy it so there :p