adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63 
Location: New Zealand
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Post by adlyman on Aug 13, 2015 18:34:52 GMT -5
Hi all,
Newbie to the forum but not a newbie to scooters. I have built a half dozen scooters to various degrees but this on takes the cake!
I have an issue with a 2010 Adly silver fox that I am modding and it is doing my head in trying to get decent top end compression I have completly rebuilt this motor including all bearings and seals I have installed a full circle malossi HPC crank with 12mm small end. Stage6 MK 2 racing AC cylinder kit. 47.6mm with single ring piston. Stage6 Pro replica exhaust Malossi carbon reeds with bigger inlet mani and the usual variator/roller mods but have yet to tune these due to not being able to obtain decent compression. 21mm Dellorto to go on but not fitted currently.
So far I have done a leak down test both in pressure & vaccume and found no leaks anywhere. Gap tested the ring to bore clearence. All good no material needed removal. 0.18mm Cylinder kit is all dialed in with 0.75mm squish clearence. Tried down to 0.6mm as suggested from Stage6. No difference. Got a brand new but cheap cylinder kit from Ebay (destined for another bike) tried that on the Adly & got 85Psi again. Tested my compresson tester against another know working one. 1 psi difference between them.
I am seriously at my witts end trying to figure out what's going wrong here but I'm falling short. Any help would be greatly appreciated. |
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Post by niz76 on Aug 13, 2015 20:50:46 GMT -5
WELCOME!!
Not much to 2t compression. Seems like you have your bases covered pretty good too. This may sound dumb but you checked to see if there's a head gasket leak?
You only make compression in the small area above the exhaust port and into the cylinder head...
Are you doing compression test with e-start or kickstart? I only do kickstart. Does the compression increase with a squirt of 2t oil into the cylinder (through the spark plug hole). Doing compression test correctly? Throttle held wide open, kick and kick and kick until gauge won't go any higher...
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adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
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Post by adlyman on Aug 13, 2015 22:59:42 GMT -5
Hi there,
Thanks for the reply.
Agreed top end compression 'Should' be pretty simple and I have never had any issues with any of my other builds however this is the first one I have done using higher end 'mid race' style parts.
Did the compression tests using both kick and e start and have had same results. Carb not even fitted so no need for WOT. Just has reed block and inlet manifold fitted.
Head has O'ring not head gasket but I will crank it up as high as it will go and use the soapy water trick to test for leaks tonight. Doubt it though as when it gets to 85psi it will hold that for ages, just will not build any higher than that!
Will give the oil in the hole thing a go tonight. Assuming this just saturates the rings and improves seal?
Here's a question for youz.
Should there be a differnce in compression with exhaust on/off and reed cage/inlet mani on/off.
Cheers
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Post by iwiketuddlz on Aug 13, 2015 23:04:26 GMT -5
Have you ran it anyway?? Just to see how it will run??? Maybe your tester is failing??? Just my 2cent!!!
And welcome!!!!
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Post by niz76 on Aug 13, 2015 23:09:38 GMT -5
I agree Tuddlz! Sounds like it might be a faulty tester. Run that baby!
Haha- in all seriousness though, it shouldn't matter whether the exhaust is on or off, or reeds in or out- only making compression when the piston and rings are up above all the ports.... It might affect the numbers a lil bit, but you should still be seeing 130 psi+!
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Post by niz76 on Aug 13, 2015 23:11:06 GMT -5
Is the tester sealing correctly against the spark plug hole? Just throwing ideas out there since you got 85psi on two different tests...
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adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
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Post by adlyman on Aug 14, 2015 4:26:46 GMT -5
Cheers for the welcome wishes.
Update:So did the oil in the plughole thing and it came up about 5 psi to 90. This approach begs the question as to why would I have ring sealing issues on a brand new kit? Is it common?
Also took the the other advice and 'ran that baby'! Used a jetting combo from one of my other 70cc's of 45 pilot and 120 main in my 21mm dellorto as a start. This is where shit gets weird. 85 psi should not start or run good but this did.....to a point.
After a quick and dirty break in (3 hot to cold heat cycles) and remember this is nakasil plated Aluminium not cast iron so I can afford to cheat a bit I took it for a spin. Power was at a ported 50cc with a pipe level but as soon as she hit 6k rpm it started to make that silly popping\farting noise. Like detonation but at the other end of the spectrum. To me there was simply not enough compression to support the sort of combustion I was asking of it.
Stepped the jetting up from 120 thru to 140 but plug just got black power dropped and it still would not pull past 6k. Also worth mentioning that this bike it totally derestricted and runs an aftermarket CDI and coil. This kit and crank combo should run 12k rpm safely all day!
Could it be that the HPC crank is making such good primary compression that its allowing the bike to operate OK at lower RPM even with such average secondary compression?
Sorry for the long post
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Post by iwiketuddlz on Aug 14, 2015 10:53:14 GMT -5
120main??? Waaaay to big IMO.... I'd try a 98 main and see what happens!!!! It is definitely odd situation you have!!!! Hope you can fix it!!!!
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adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
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Post by adlyman on Aug 14, 2015 15:58:14 GMT -5
Yea this whole compression thing is super weird.
Dropped the jetting as low as 1.05 main but was dangerously lean. It would be insufficient if it was running like it should. I'd guess its sweet spot jet will be between 1.15 and 1.25 I`ve found that the dellorto's I run on my bikes here in New Zealand seem to like to suck a fatter jet than a comparable size Keihin or PWK. Our weather is very changeable here too!
Will keep trying to find the issue.
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Post by niz76 on Aug 14, 2015 18:16:01 GMT -5
popping farting noise... o ring head *gasket*? Any signs around the head of leakage now that you've run it?
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adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
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Post by adlyman on Aug 14, 2015 19:06:52 GMT -5
No mate. None at all. Used soapy water in a spray bottle when it was running and soaked all round the head area. Did a 'hot' compression test too and it was still under 90 psi.
Noise at 6k rpm is definitely inside the motor. It just wont pull past 6k, bogs down and makes da noise like its struggling.
Got another mate coming round with his compression tester for 1 more check to make sure mine is working like it should but I'm pretty sure mines fine.
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Post by iwiketuddlz on Aug 14, 2015 22:13:13 GMT -5
Imperfection or hole in the piston??? Check that sucker with magnifying glass!!!!
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adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
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Post by adlyman on Aug 15, 2015 0:27:03 GMT -5
Yea. I think at this stage I've tried all the usual's so it maybe time to go all the way back to the beginning and start again. Cheers 4 the help. If I find the problem I'll report back.
Cheers.
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adlyman
Scoot Member
If you ain't pushing it, you may as well be pulling it!
Posts: 63
Location: New Zealand
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Post by adlyman on Aug 15, 2015 0:31:55 GMT -5
Oh yea and my compression tester matched my mates one that just had a calibration (used in a bmw workshop) so she's readin fine.
Cheers.
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Post by bugboy1641 on Aug 15, 2015 5:25:05 GMT -5
Can you get your hands on a cylinder leakage tester?
Compression testers are ok but a leakage tester will tell you where the leaks are.....
Where in nz mate?
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