adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Aug 16, 2015 2:35:23 GMT -5
Hey bugboy. Already done a full leak down test dude. Did it in both pressure and vaccume and found no leaks. She held 7 psi for over 4 minutes and 6 units of merc vac for over 3 so no issues there!
I'm in Feilding, Manawatu. You?
|
|
|
Post by bugboy1641 on Aug 16, 2015 14:49:09 GMT -5
Auckland mate, I'm new to scooters but wish I'd bought one years ago, best way to get around the city. I'm a mechanic by trade so know how an engine works but limited on scooters. what about a restriction in the intake? That'll lower compression.
|
|
adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Aug 16, 2015 20:49:36 GMT -5
Hey dude,
Yea I was a mechanic for a few years too. Much like you I know the fundamentals and scooters especially 2 strokes are about as simple and cool as it gets. There must be something that I have done or not done that is leading to this not working properly!
I have done compression tests with the inlet mani and reed cage completly out so the inlet is as unrestricted as it ever going to be!
The only other newish thing to me is that this Malossi HPC crank has a standard stoke but a longer than standard conrod. This has meant that I've had to space the base out just over 5mm using a laser cut aluminium base gasket with a normal paper gasket on each side. I believe a normal conrod is 80mm so I presume that this one is 85mm. Very hard to measure once installed!
This will obviously have an effect on port timing(loose low end torque but will rev higher) but as I understand it, provided you have set up the squish correctly this should make no difference to top end/secondry compression?
|
|
|
Post by ryan_ott on Aug 16, 2015 21:12:45 GMT -5
I would think a cylinder to piston clearance issue, too much clearance causing leaking by rings.
|
|
adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Aug 16, 2015 21:28:22 GMT -5
Yea Ryan,
That has been my thinking all along to but on a cylinder kit where the piston, rings, cylinder and head are all brand spankers this shorly has to be highly doubtful.
Checked the ring gap in the bore before fitting and it was bang on using the 0.004" per inch of bore. Mines a 47.6mm job so the gap worked out to 0.008" or in my part of the world just under 0.20mm.
This kit uses a single ring race piston from Stage6 so to prove this very point I went looking for a double ring piston in 47.6mm but could only find them with 10mm wrist pins not 12mm as I need. Also looked into the Stage6 10-12mm bearing converter but my Malossi crank's small end has a 16mm diameter and the bearing converter has a 17mm diameter. No way was I going to mill 1mm out of a high end crankshaft just to prove a point. Only now I'm thinking twice about it! lol.
|
|
|
Post by katastroff on Aug 17, 2015 9:16:54 GMT -5
I'm not one of them big tuning guys, but i know there are some engine kits where you can buy a new piston of a different size. ( Piston A,B or C)
Maybe you got a mix matched set?
|
|
adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Aug 17, 2015 17:11:17 GMT -5
Good Point mate!
Had a look and it has 'A' on the piston/ring set. I'll do some more research and find out what the differences are between them. I'd doubt they would be oversize as to my knowlegde you dont hone out a Nakasil lined cylinder, just get a new one.
Very hard to get good info in New Zealand. Scooter tuning is not big here. Most dudes just buy a stock scooter and go A to B on it till it dies then get another one! All our stuff is imported and there's only a couple of companies that specialise in the performance side and I dont live close to either of them!
Thanks for the info.
|
|
|
Post by katastroff on Aug 17, 2015 17:56:19 GMT -5
I'll send a mail to our head office and see if i can get you the info.
Edit: Mail sent, i should have the reply tomorrow.
|
|
adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Aug 17, 2015 21:14:33 GMT -5
Much appreciated katastroff.
Cheers.
|
|
|
Post by katastroff on Aug 18, 2015 3:34:46 GMT -5
Got the reply.
The piston A, B and C are 47,6 + 10 thousandth for each letter.
That's if i understood the reply i got correctly.
Do you have a way to mesure precisely the size of both piston and cylinder?
|
|
adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Aug 18, 2015 16:59:51 GMT -5
Hey Katastroff,
At home I only have a decend set of vernier calipers but I work in Aviation and there are some super nice bits of measuring kit in the machine shop so I'll go back and see them boys.
I already took the cylinder to them once and we checked the cylinder for concentricity and ovality as I wanted to make sure it was not warped or out of round. Like maybe a casting error that slipped through quality control but it was some stupidly small amount out. The machinest said that they would accept those tollerences in aviation! We did not measure the actual cylinder diameter though and I assume we would need to measure multiple area's up and down the cylinder to get an average.
I'll measure my piston tonight and see what that comes out as.
Cheers.
|
|
|
Post by katastroff on Aug 18, 2015 17:11:07 GMT -5
|
|
adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Aug 20, 2015 0:42:27 GMT -5
Just to update, I have sent this bike all setup off to an experienced scooter modder for him to look into. He's going to ride it 'as is' then pull down checking all my work & clearences and see if he can find the source of this low compression issue.
Always good to get another set of experienced eyes over a problem. Hope its nothing too simple otherwise I will have to administer myself a beatdown!
|
|
|
Post by iwiketuddlz on Aug 20, 2015 4:25:26 GMT -5
I have to admit I have been beaten a time or ten!!!!good luck bro!!!. I'm very curious to the culprit......
|
|
adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
|
Post by adlyman on Sept 16, 2015 20:26:03 GMT -5
UPDATE: Had many a late night with my mate in the garage putting stuff on and off and spending more money on parts but we finally cracked it. Long story short and probably a good lesson for all is that not all manufactures parts will work well together even when brand new! Compression wise we changed pistons from a Stage6 RT 'A' to a 'B' and we found 130psi! Yea, all good. Tuning time and beers to celebrate. BUT After days of tuning we could not get this setup to go anywhere near as hard as it should. It would rev out slowley but never really 'power band' up like my mates one with the same cylinder but a different crank would. So I removed the hellish expensive Malossi MHR crank and imported a matching Stage6 HPC crank with standard 80mm rod length from Scooter Attack and boom, hits 7k rpm and goes nuts right to 12K hard and strong. Would go harder but the limiting factor is that I only have the stage6 Pro 'replica' pipe which is a 'mid-race' setup on top level A/C cylinder. We are still confused as to exactly why the Malossi crank would not run right with the Stage6 cylinder? It had a longer 85mm conrod but the cylinder was spaced out from the base with an alu spacer plate so everything should have been good. We could only think that due to the mismatch of parts we must have been throwing the port timings off just a whisker but it was enough to stunt the performace of the cylinder down to like an entry level street 70cc kit. Very happy with it now though, but it bloody well should be with how much money its had spent on it now! lol.!
|
|