T500 Special Engine (Ported) Rebuild
Posted: Mon Oct 03, 2016 6:41 pm
Ok guys I don't really know where to start but here goes; some of you already know me and my bike from another forum dotheton (hope that's ok to mention it here). A couple of years ago I built a custom t500 with modern suspension and modern geometry with a mildly ported engine and hand made pipes. It is a 1972 chassis but I think the engine is 1975 as it has the electronic ignition. Unfortunately I never did get it running right so I am going to completely strip the engine again and totally rebuild it. Last time I didn't have the crank rebuilt because po said it had been done recently. I now believe that was not true.
Biggest problem I had was that it ran like it had an air leak, when you revved it up it the revs didn't die down right away. If you are able to watch this clip https://www.youtube.com/watch?v=5p8GTQr2kE4" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false; on youtube you will see what I mean. Eric I think the owner of this site did the porting to hopefully achieve 55hp, I am running 34mm mikuni's with custom pipes that I built to specs (using all my engine info) from I think another member on here Teaser.
I must confess that I short cut the original rebuild and now regret it. After Eric did the porting I was going to have the cylinders bored to next size over (max) and fit new pistons (i bought some on ebay for $60 brand new) but I just ended up putting new rings in it. Also I never skimmed the 0.020" off the heads that Eric suggested.
So the plan now; Strip engine completely and have the crank split and install new center seal. Buy new forged pistons (max oversize) and get cylinders bored. I need to know what clearance is needed on the bores, planning on 0.0025". Skim 0.020" from heads. Of course I installed new outer crank seals last time I rebuilt it but I will put new ones in anyway. I plan to use Bill Bune to do the crankshaft and boring unless there are any other suggestions here? I will do the heads myself.
I want to do this right this time so if anyone has suggestions for anything else I should consider doing while building the engine fire away The bike will run on Sunnoco standard leaded race gas (no more ethanol crap for me )I am building this bike to use mostly at trackdays.
Just drained the oil out before I remove the engine and it is about 50/50 oil and gas (petrol).
Biggest problem I had was that it ran like it had an air leak, when you revved it up it the revs didn't die down right away. If you are able to watch this clip https://www.youtube.com/watch?v=5p8GTQr2kE4" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false; on youtube you will see what I mean. Eric I think the owner of this site did the porting to hopefully achieve 55hp, I am running 34mm mikuni's with custom pipes that I built to specs (using all my engine info) from I think another member on here Teaser.
I must confess that I short cut the original rebuild and now regret it. After Eric did the porting I was going to have the cylinders bored to next size over (max) and fit new pistons (i bought some on ebay for $60 brand new) but I just ended up putting new rings in it. Also I never skimmed the 0.020" off the heads that Eric suggested.
So the plan now; Strip engine completely and have the crank split and install new center seal. Buy new forged pistons (max oversize) and get cylinders bored. I need to know what clearance is needed on the bores, planning on 0.0025". Skim 0.020" from heads. Of course I installed new outer crank seals last time I rebuilt it but I will put new ones in anyway. I plan to use Bill Bune to do the crankshaft and boring unless there are any other suggestions here? I will do the heads myself.
I want to do this right this time so if anyone has suggestions for anything else I should consider doing while building the engine fire away The bike will run on Sunnoco standard leaded race gas (no more ethanol crap for me )I am building this bike to use mostly at trackdays.
Just drained the oil out before I remove the engine and it is about 50/50 oil and gas (petrol).