Project Cafe Rocket 686 begins. Finally!

[Srinath]

Oooo its backwards, not from suction in the piston, its from the crankcase pulses ?

OK sorry I'll call small BS on that one, cos the crankcase has a vent - but sudden surges can affect ... That makes me wonder about something else. On a GS500 the crankcase vent is in the valve cover. Maybe that is a better design, on this guy its in the left side bottom part behind the starter right ?

I'll ask my engine guy. He oughta know. He said fitting those were a blatch.

Cool.
Srinath.

[edfmaniac]

I probably am mistaken about why the oil is coming through the valve seals more with the TS rings but there are plenty of people who mention it. Seems to be more of a problem at low rpm. Either way, I wouldn't use them if I were assembling the engine. Maybe if your engine guy does all of the measuring and end gap filing, you can get them to work for you. I'm from the KISS school of philosophy. Keep It Simple Stupid

[Srinath]

I am from the "I aint buying crap while there ois perfectly good crap sitting right here" camp.
All the piston kits have rings included ...
So No Total seal.
My guy has experience filing those though, but I am just going to use wiseco/JE ones.

BTW I am finding wiseco in 10:1 easier than JE. If JE dont turn up quick Wiseco it is.

Cool.
Srinath.

[edfmaniac]

Time for the Mikuni fantasy to come true. But instead of going with the twin 34mm carbs, Topham is putting together a TM34/38-B65 for me which has a 38mm on the right side. Bill would probably scold me but the red blooded American in me said why not put carbs on there that match the respective port sizes instead of having a 34mm carb bore just dump into a 38mm+ port without any kind of aerodynamic transition. I may lose some street friendly characteristics but the top end is going to be insane. Assuming the stock carbs were my problem with maintaining combustion above 7400rpms, I expect to hit the 65whp mark easily. That's what my gut is telling me. Cost isn't cheap but only a few more euros than the regular TM34-B65. Expect to see pics within a month.

[zippy49]

Better double check the compression ratio if you go with Wiseco...I once had a top end done with a Wiseco 102.5 mm piston on my XR650L. It was marked "10.25:1" right on top, but checked out at the stock 8.5:1.

[edfmaniac]

The final compression ratio depends on how the engine is put together. If you leave a huge squish, your ratio will drop. I measured everything that I could and tolerances are at a minimum so I should be close to the advertised ratio. Even if it's 10:1 now, that's fine with me considering the dyno results and massive change in power delivery.

[Srinath]

I will have the guy measure the ratio after assembly. He said he can ... while he is at it I'll take the black mz over to have him measure it too, as well as weld the can on etc.
Cool.
Srinath.

[Srinath]

The wiseco 102mm piston looks well, less aggressive than the JE did. Basically the top is flat with 5 small valve cut outs. The JE was far more dome like with larger valve pockets. Wiseco is supposedly 9.9:1. Hope it works good.

Cool.
Srinath.

[edfmaniac]

Feels like Christmas! I just ordered my Mikuni TM34/38

[den]

i remember one the the first posts was advise on how not to get carried away,,lol,,bloody hell mate,,tot it up for me including you man hours.$$$$$$$$$$$$,,How much have you spent so far,,well done for what you have achieved but start a new thread soon

" Project Cafe Rocket 686 is Finally Finished "

( anyone wanna buy my house i'm broke ),

[edfmaniac]

Nowhere near finished! I still have a lot more time and money to put in. It's a hobby so I don't worry how much money gets spent as long as it's enjoyable and I can still put food on the table and pay rent. No kids or wife! No wardrobe! And no debt! All my consumption is focused around eating and building motorcycles for the foreseeable future.

[Srinath]

Oh the wiseco 102 I bought has a dome-pin height of about 4mm less than the JE that was removed.
So I am going to have a big drop in CR ... from how much to how much ??? No clue.

Anyway the Wiseco is also larger than the bore ... like its too tight in the bore. The piston may be a B or a C piston, my guy is happy with that, and so am I, I was worried that it may be too small. Like I had a loose 102 cyl cos it has run 102 in it for over 10 years. The JE was a 2004 or earlier piston. So my fear was I'd not get a piston to fit right ... no worries there, its a good one now.

Cool.
Srinath.

[edfmaniac]

To be honest it sounds like your engine builder is chasing his own tail. Either that or there is a communication problem. The piston is larger than the bore? It's supposed to be if you are going to have the cylinder machined to fit the piston. If you aren't, find another engine builder and start over. I'm a complete novice with only general mechanical skills, and was able to build a heck of an engine with the help of the internet and a few good machinists. No guessing!

[Srinath]

No, I didn't explain it here too well.

I had a bore that had a JE 102 in it. Obviously that bore was machined for that piston, so it was @ 102 long before I ever got it.That was the one that was busted etc etc ... He cleaned up the bore - obviously as lightly as possible. If I got that same JE piston, I'd have had it loose in the bore - may have fit it OK but loose.

The Wiseco I got fits in the bore but is a lot tighter than the pre existing 102 bore for the JE. They make these pistons in an A, B and C size. The seller of the wiseco was dealing with some old stock, and was not sure what he had etc.

I got lucky, and I now have a B or a C 102 piston and I just need to hone it a wee bit.
So we're not getting confused by what I am doing, just that I am haphazardly explaining it here.

Cool.
Srinath.

[Srinath]

I am reassembling it now. The weird thought I had was ... if we deck the head, and other wise reduce the squish height etc, how can that top cylinder cover mount still fit ? I know we have to accomodate the cam chain when we reduce the squish height, but this bike has that thing on top.

BTW, my head cover mount had broken. Maybe that was why.

Cool.
Srinath.