Bike was running hot, found out why....

[Oilyspanner]

 

Thought I'd better share my error with everyone, I had been asking Jonny1Bump a few questions on his excellent build thread, but I don't want clog up his thread with my 'stuff'.

My bike has a big bore kit fitted, ported head, de-shrouded valves etc. I spent loads of time trying to get everything as good as I could/was able. After 150 miles of piston ring/bore bedding in I changed the oil and filter - thought I'd check the cam timing at the same time.... found they had shifted from 105 centres to over 110 ! After finding true TDC I left the bike over-night and adjusted cams to 105 degrees the following day. I used the bike on a load of shortish trips over the next few months, was mega torquey, but during the hot weather in particular it was prone to pinking at the bottom end.... bugger !

Did the normal stuff to prevent pinking, but it didn't go completely - Jon said to retard the intake cam a few degrees, which should help. Anyway, it turns out that both cams were advanced by 10 degrees, that'll make it run hot !! - I think my crankshaft position pointer got snagged by someone going past the bike to the freezer - should've double checked TDC again... I will in the future, first time it's happened. I've since altered the cams and the engine feels less 'barrel chested' in delivery, but is smoother, revs harder and really shifts from 5k up - strong from 3k up , gets fruity at 4k, but the big torque and impressive power is from 5000 revs..... oh and it doesn't pink !  and obviously the cam sprockets hadn't shifted in the first place, lucky the pistons hadn't clipped the valves, must've been getting close - probably a good thing that major shove was available below 7000 revs at the time.

[jonny1bump]

Got another tip for you undo single cam sprocket bolt at a time and fill slot with green Loctite being really careful not to fill engine with it. If bolts come loose most cam timing will move is half a degree. At least you have explanation for the strange behavior. To be fair you should check piston to valve clearance.

[Oilyspanner]

Yep, pleased I found the reason Jon - wish I'd measured the p to valve clearance, would've shown something wasn't quite right too, I fitted new valve springs too, which probably helped avoid contact.  I'm thinking about fitting larger inlet valves next, I'll definitely check the p to v clearance then. There's a company called G and S valves, who have 30mm inlet valves for M/N listed as the same weight as std 28.5's, so I could get more inlet charge into the cylinders and use std springs, so no additional wear on cams and losses due to harder springs...sounds like a plan, got some KibbleWhite guides on the shelf already...hmmm. 

I had the fuelling pretty rich for running in, I set the jetting after doing the oil and filter (and setting the cams - wrongly !).So it's only just recently I could feel the new power properly - it's enough to make me feel like fitting the steering damper again, getting crossed up by unexpected air time off bumps is a little too close to a proper shake now. The engine has lost some of it's low end grunt (compared with the 'advanced' set-up), but it's properly quick now - really impressed with the old girl - old GSXRs rock - will put a smile on your face and will want to kick other bikes in the nads … !

I haven't used green Loctite (haven't got any), I used permanent , but I did find out about doing one bolt at a time, oh the fun I had finding my new settings had moved before hand !

Thanks for the suggestions Jon 

[Oilyspanner]

Just to put my mind at rest I've checked the valve clearances, any valve deflections should show up - I last set clearances before I accidentally advanced the cams and much to my relief they're the same - result !  There hadn't been any odd noises, or drop off in performance, but it was still best to check. 

With the cams properly set I've found that by lifting the needles a notch I've gained some more pick up as soon as the needle region starts to influence the mixture - carries on strongly too, not too different to the advanced power now, but it runs cooler, revs more readily and definitely pulls harder at the top, a lovely motor - just have to make sure I don't kick the crank position pointer/lad's ball knocking onto it/wife barging past it tutting, whilst I'm doing stuff in the future ...

[jonny1bump]

Time to stick on the dyno now then.

 

[Oilyspanner]

I might do that Jon, always good to make sure AFR is good, have a look at the shape of curve , seeing where improvements could be made -  plus if I do go down the larger inlet valve route it'll be interesting how much is gained and where... then it'll be flatslides, directing more cool air to the airbox, getting an ally tank made and asking Jonny1Bump if he's got any CF bodywork ! - damn, thought I was done....