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Post by 90GTVert on Apr 1, 2011 20:44:57 GMT -5
I got some compressed gasket material and made up a new base gasket, then pulled the engine apart again. It had what looks like Ultra Grey Permatex for a base gasket. I cleaned it all up, and got to take a look at the ports. I was curious if anything was done, since this was a custom build. Looks like a stock style crank and basically just enough work to fit the cylinder. They attacked one transfer with a dremel a bit, but nothing that would put this beyond a stock 90cc. Cylinder looks pretty standard too. The base gasket upped the squish clearance to 1.49mm and cranking pressure lowered to 150 psi. Sounds more reasonable now. I couldn't find my old rollers, but since ltsride and lauderdaleboats both reported 6g rollers stock in their 90s, I went with those. I also pulled apart the rear pulley and found a 49cc contra spring, so I swapped in a 90cc contra. Here's the difference in the two (90 is on the right). I got the brake parts in from 2strokd today (thanks!). I swapped the shoes and springs from T1's engine on as well. I'm thinking about taking the center stand off of T2's old engine and putting it on here, then maybe getting the stand from a short case for T1. I think the short case mina stand might be better for the lowered scoot, not sure.
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Post by 2strokd on Apr 2, 2011 9:55:21 GMT -5
Thats awful close to that stud hole huh? WoW Good thing you did a pre-inspection on the that!
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Post by stepthrutuner on Apr 2, 2011 10:37:21 GMT -5
Yeah. I'd be reluctant to put any extra torque on that baby.
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Post by 90GTVert on Apr 2, 2011 13:18:43 GMT -5
I torqued it to 13ft-lbs instead of my usual 15. It's all back together and in T2. I used the stock exhaust from the 49cc Venus, as it's the smallest of my stock pipes and the original Triton pipe was modded. The Venus pipe did have an emissions tube coming off of it, which I hacked off and welded up. I painted it for that reason, and to get rid of the chrome on the cover. Paint dried gloss, even though it's flat, in spots. Tried to re-coat to no avail. Luckily, the plan for this thing is testing and then back to the parts pile. I still need a few parts and I still have to wire in a connection for the enricher, but I should be putting along soon. It's been a long time since I've rode one with a stock pipe. Should be torquey at least.
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Post by lauderdaleboats on Apr 2, 2011 19:02:46 GMT -5
165psi cranking compression. I get the feeling there's detonation in my future. Re: That unusual head design. Are you getting 165PSI with that head? I checked my compression today using that same head and had 80PSI. That's just reassembled with now 2mm up on the exhaust port. I put the head in the mill and cut that funny squish area till it disappeared then decked the head 2.5mm. It now looks like a stock 54mm head. Re-installed the head, checked compression. It's now at 140PSI. This made a massive difference. I would spin up to 7500RPM before. With this change, now spinning just over 10,000RPM and the power is unbelievable. I didn't have the GPS but it is 'smokin' compared to before this change.
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Post by lauderdaleboats on Apr 2, 2011 19:06:32 GMT -5
Just to give you some idea of how much material I removed. See those 4 little 'nubs' forward and aft of the stud holes? Approx 1/2 the height of those were removed when decking the head.
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Post by lauderdaleboats on Apr 2, 2011 19:10:51 GMT -5
Quote:I put the head in the mill and cut that funny squish area till it disappeared then decked the head 2.5mm.
Sorry, 3.5 mm removed during decking.
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Post by 90GTVert on Apr 2, 2011 19:21:24 GMT -5
Well, 150psi now that I have a base gasket, but yeah the stock head. No mods to the head. Thin copper head gasket.
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Post by stepthrutuner on Apr 2, 2011 19:44:43 GMT -5
Cool the way you're doin' this one.... bone (practically) stock to who knows where. Should be a very valuable tutorial for tuners.
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Post by lauderdaleboats on Apr 2, 2011 20:32:01 GMT -5
I must have some sort of issue going on inside the motor, broken ring maybe. I never checked compression till today and the scoot has been running pretty much the same since I initially put it together. I was pretty shocked I only had 80PSI. Took the head off to see if the cylinder was scored or damaged but all looked fine. I was about to do a complete teardown and get started on my build. I had the head in my hand and thought lets make this right and give it a try.
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Post by 90GTVert on Apr 2, 2011 21:05:57 GMT -5
80psi definitely sounds like there was something wrong. Did you measure squish when it was at 80psi or now?
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Post by lauderdaleboats on Apr 2, 2011 22:56:28 GMT -5
I didn't get too deep into this motor but the piston sits 1.7 mm under the deck.
After removing 3 mm of material from the head the fly cutter just started to touch that 'hump squish ring' in the head. Then cut an additional .5mm which removed .5 mm from the hump ring. I then used an adjustable angle cutter in the bridgeport and cut the hump away to match the dome of the piston. That was an additional 2 mm. Considering the outer edge of the squish band is just over 1mm deeper than the deck, the thickness of the head gasket, and the 1.7mm piston to deck clearance I'm probably still looking at close to 3mm squish.
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Post by lauderdaleboats on Apr 2, 2011 23:05:04 GMT -5
I shouldn't be posting this stuff on your build thread. I'll copy and paste it to the Baccio build. I'll delete them from here then.
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Post by 190mech on Apr 3, 2011 5:34:48 GMT -5
Was that an original 90cc motor or did somebody mod 50cc cases with a chain saw?? ;D
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Post by 190mech on Apr 3, 2011 12:21:08 GMT -5
Brent,Did you check the final drive ratio yet??
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