Guess I should call thread ... 2016 rebuild, Ive been doing the engine in a seperate thread so its easier to search should anyone be doing similar in the future. Nothings been done on the rest of the bike for a while.
Lastest work, alt cover painted and on, oberon clutch slave in place, painting heads then rebuild them.
Thanks Sev, VHT flame proof. Its a goldy bronze colour, meant for manifold etc 1000 degree resistance, gonna have black covers on it.
Made these out off stainless bicycle spokes for the cables and vent lines on the lower of the engine, came out well.
Buy off ebay from far east, very cheap, heat and bend round 6mm bolt and steel bar then polish to get off the heat discolouration.
I used the very top of old car aerials (which I had collected over the years when changing from ordinary pull out ones to electric ones)
Lapping valves then rebuilding heads, measured squish on this front cylinder and Im going without base gaskets on the barrels as its coming in at 1.6 on average across piston. Made my own head nut tool out of an old spanner and socket.
Thanks Sev, I'll take a picture of the can. Its flameproof paint I bought for the headers, but since I got the Sil downpipes Ive used it on the heads, its a really nice colour, like a darker frame bronze. Its up to 1000 degrees C!
What's the squish at the edge of the piston? - that's the important one. Sent from my P01M using Tapatalk
That seems quite wide - the JE's should be matching the originals and giving a value nearer to 1mm at the edge. At 1.6 you're not going to get the full benefit of high compression. Not that it's any help, but reducing the deck height usually means machining the barrels. Sent from my P01M using Tapatalk
When I was about 14 a guy I knew that built speedway and grasstrack bikes (usually with J.A.P. engines......so that's a long time ago) used to measure compression ratios using oil and large syringes...... ..........he would fill the cylinder at BDC with oil from a measured amounts in the syringe, and did the same with the upturned head (valves in, of course).....that way he could arrive at the total and swept volumes. He would measure the stroke with a dial gauge supported on a flat bar across the cylinder gasket face and he would measure both the crown and the circumference of the piston. He rarely included the head gasket. Having done his calculations (usually on the back of a fag packet) and if he was satisfied he was going the right way; he would complete the build and then fire it up on a bench.......he would eventually use a compression tester and normally got as near as dammit the same reading as his calculations suggested.
I used silly putty all the way around the piston edge and over the top in a cross. IIRC the base gasket is about 0.3mm These pistons are a straight swap for the originals, so what am I gonna need to measure the volume for? Surely I can check compression when its together and if its a problem take the heads off again. Do JE not work this all out before they sell their products??
Sev, they are high comps. From what I have read they should drop straight in. Some use base gaskets and some do not. I am not planning to take it to the track, its not a race engine I just want a little more torque, I realise I may have to change the timing but is it neccesary to start machining brand new pistons for maximum flow and squish as I have read? I do not have the money at the moment to do any head work porting and polishing etc.
They guy I mentioned who built the speedway bikes said he didn't bother with the head gasket when measuring volumes because it didn't make much difference to the end result - unless it was necessary to stop a piston hitting something and if it was that close to doing that; he had done something wrong anyway.
Gents, thankyou very much for your help, its much appreciated, I was starting to worry about how much work these pistons could cause me but you have reassured me. I can predict me running it a bit then perhaps doing more work later on. This was originally taken off the road as it was burning oil due to valve stem oil seals. The rear head was fouling plugs very quickly and blue smoke. So far its gone from head rebuilds to bottom end, to high comps, lightened flywheel, full maxton suspension front and rear, upgraded rectifier and ignition plus Sil downpipes! Add that to what I had, full Ricambi bodywork, single seat, Sil carbon cans, Keihin flatslides so the only thing missing is the magnesium wheels..... Very similar to the SS I nearly bought from you Sev.
