Venus 50 (Now 96cc!)

[90GTVert]

Just went and checked the 2nd ring. It's worn badly as well. Also over .025"

[190mech]

Heck,it could be that the rod bearing particles have imbedded themselves in the bore also!Those vertical scratches mean something has been chewing away at it..Maybe it is time to try another cylinder..
I forgot about the cramped cowling around the engine,guess some more needle and jet tweeking might help it..
Do you have a Cylinder Head Temp gauge you could try?

[90GTVert]

lol No. I've never took the plunge and bought one like I know I should. All I can tell you so far... it's been HOT. Wonder how hot is has to get to diesel?

I was thinkng that with the particles or whatever in the cylinder. I mean, it's hard to believe it could be honed 3 times and have something there... but then it's hard to believe it would be killing rings in 5 miles or so 3 times since a rod failure with lots of debris for any other reason whn you look back at exactly when it started doing this.

[190mech]

While web surfing last night reading about bad 2 stroke street bikes(I want an RD350 but dont need one..),there is always a mention of retarding the ignition timing after a compression increase.Have you tried this yet?They are talking about stock is 2mm BTDC,modded 1.6mmBTDC,supposed to keep it cooler,might be worth a shot after you have the cylinder issue corrected..

[90GTVert]

I've never messed with the ignition timing on any of my 2Ts. My timing is retarded on the SunL though to keep the spark knock away. I might have to give it a shot. I've never heard timing specs listen in mm. I assume that means you would measure the piston's postion below deck and set the trigger up to fire at 1.6mm BTDC. I'll probably just mod the pickup's bracket, which is good for roughly 3 degrees either way on most of the small engines I've messed with.

[90GTVert]

I stuck the engine mostly back together this morning. I put the stock cylinder and piston on in it's stock configuration with the stock head and all. I have a brand new 54mm cylinder kit here, but I wanna see what happens on the stock stuff before I go tearing it up. Compression might really be a big issue. I got about 185psi on the last setup. The stock setup makes 100-105psi lol. Maybe I was where I needed to be getting 140ish psi on my other setups?


Also, I got this back from VT when I asked for any more details abotu the pipes they sell. I think the carb sizes are a bit off.. I don't think you have to go all the way to 28mm necessarily, but here's their info...

"Hey Brent,

I think the Phongeer Black with the Carbon Fiber heat shield would be the way to go. If you run the full expansion chamber pipe with out at lease a 28mm carb, you will over heat and seize the bore.

The Phongeer is a Performance exhaust is made for BWS 100cc and bigger. Big inlet, large size header pipe and tuned for more speed and torque. It is not just a 100cc muffler. This pipe just came out last month and there are only two here in Hawaii. The other one I sold to my friend on Maui who has a Zuma 50 with a 100 engine on it. He is about 300lbs and cruises easily at 55mph. But says it has much more pull, just that he is breaking in the new cylinder. It's bigger than stock, but I don't know what size it is. He bought the larger cylinder from the guy who brought in the ZUMA / BWS 100 engines from Taiwan. I know he is running the stock carb that came with the engine, but plans on going with a OKO 28mm or 30mm carb.

Talk to you later,
Steve VT
www.vtcycles.com

P.S. I just called my friend about the Phongeer ZUMA 100 black exhaust and he said it makes a little more noise than a muffler. Kind os a "pank pank" noise, but he likes it. Power with stealth as he puts it. "

[90GTVert]

I got the engine back in. I changed the main jet from a 90 to a 95, on top of moving the neddle up earlier. It's too rich for sure. It breaks up and struggles a little to rev. I rode it about the same distance and heard no crackle of spark knock. The engine actaully turned off when I killed it too. It could be the excess of fuel cooling it, but I think a lot of it is compression. It did about 43MPH running the test strip all the way out instead of letting of early at 50MPH. On a straight stretch I managed a whopping 48MPH sitting up. Needless to say, I can't wait to get it properly set up and tuned. The minor difference in displacement isn't much, so I'd say it shows how much difference you can make when you set a cylinder up properly... sorta lol.

Oh, also there was no engine knocking this time. ;D

[90GTVert]

After it cooled down, I pulled the motor back out and tore it down real quick. I had installed a fresh spark plug to get a read on it this time. It's wet around the ring and the porcelain has plenty of color.



The cylinder head is wet and basically clean, and the piston is a little wet and dark.



I didn't get a pic that turned out very well, but the cylinder did show some mild signs of scuffing still. I think I'm gonna make a fresh batch of premix incase I was a little lean on this last one. Not to mention it's a little old. The rings weren't all worn out this time either. I think if I get it set up right, I should be OK with this carb from what I've seen. I think I might still go with an exhaust from VT or somewhere to have a stealthy pipe that is intended for my displacement. Even knowing the SP3 wasn't the problem, it will keep my mind more at ease with a 90cc pipe. Not sure if I wanna go with VT or the LV from SIP (that's a lot of initials). I'll have anothr look around, but I'm kinda inclined to go with VT at this point just for the good service. My wallet isn't fat though, so I'll see what the price differences are with shipping and all and what other info I can find. My Leo isn't bad, but I need a pipe for T2 and it's still a little loud. It's also obviously an aftermarket pipe at a quick glance.

[190mech]

Looking back at your port timing for the stock 90,you had 182E and 120 T(2 base gaskets).Do you think the piston crown could be filed as you did on the 54mm to approach 130T?That way youd have a stock tuned 90cc to have a base line..What about running that milled down 54mm head too?
You know Im a pipe fan,the muffled LV from SIP will never give you the performance of a full expansion chamber and the LV will hold back future mods too...

Edit;The old school stuff had points ignition and we would use a dial indicator thru the plug hole to set them,just wanted to show how little a change would make an engine perform better and run cooler too..

[90GTVert]

I've got some updates on the engine, but it's midnight and I'm too tired to post anythign good right now. I will post the response I got from the eBay seller that I linkedto earlier, selling a tuned piupe for 70-100ccs. I asked simply what the diamter of the stinger is, and this is the reply...

"The diameter of the stinger (header pipe?) is 29mm."

It's always good to know your products. lol

[90GTVert]

When I ordered seals to replace the one I needed for this engine a while back, I ordered 2 54mm cylinder kits. Theey were a reasonable price from the seller and I have noticed 53mm stuff getting more popular and 54mm stuff becoming more scarce. I have this engine, T2, and T1 that all will use 54mm cylinders so I figured even if my last cylinder had turend out alright, they'd be needed at some point. I got them from kaseaparts.com. They don't include cylinder heads, but I was pleased that each kit comes with 2 base gaskets.



While doing one of many partial assemblies, checking timing and filing the piston, I torqued down a spacer used to asseble the cylinder without a head in a bad position. I heard a snap and found that I had broken the edge of the cylinder off.



I welded it back on and ground it down. Please forgive the weld imperfections. I kinda wanted to re-weld and re-grind, but I don't like the risks of grinding too much off of the deck and those imperfections loolked like they'd still allow me to seal the cylinder fine.



After the intial smoothing, I used sandpaper on glass along with 60 and 80 grit sandpaper to try and true the deck up better. The first pic shows how it started. The second pic shows how it ended up. There is still a slight low spot indicated by the marker, but it appears to be sealing.





After that was taken care of, I went back to working with port durations. I ended up at 184 exhaust and 130 transfer again by filing the piston. It started out at 178/118 stock.

Once that was finished, I started checking squish and compression readings. I think my compression tester may have been reading low in the past, but I'm not sure. I noticed that the rubber seal on the tester was in bad shape and swapped it out for the crush ring from a spark plug.

My first test was with no head gasket. I came up with about 1mm of squish clearance, and a compression reading of 210psi that surprised me a bit.



I moved up to my thinnest head gasket and came up with roughly 1.25mm of squish clearance and 202psi. Then I moved up just above the widely approved setting to 1.45mm, and still came up with 188psi. When I tried to look up stock 90cc ATV specs, it sounds like a fresh stock engine should be 120-130psi. I guess I might have to dig out the cylinder head that I had modified for T2 to drop it's compression. When I was first building T2, I never checked compression with a tester. Wish I did now.

This build has been interesting to me to say the least. lol

[90GTVert]

I did some checks with the modified head with the 11cc combustion chamber to see what that got me.



I started working backwards, from most to least squish.

1.75mm = 130psi
1.6mm = 138psi
1.3mm = 148psi

I went with the 1.3mm setup (no head gasket). 148 should be safe, but still higher compression than stock. I kinda wanted to see a higher number... but I kinda don't wanna melt stuff. I put the needle clip to the next to richest position and went back to the 90 main jet.

I took it for a trip into town and never heard any obvious spark knock. It also shut down immediately when killing the ignition. Those are two good signs anyway. It is definitely a little lower on power than the best setup, but then again it's probably 50+ psi lower on compression. It will still easily lift the front wheel on a launch, and effortlessly gets up to speed in town. I got as high as 57MPH when the cars in front of me decided to hit their brakes hard enough that I struggled to slow down with them lol. I removed 1 spacer from the variator before the engine went back in as well, because when I checked it had enough clearance to move off of the guides in the variator. That means the belt isn't even all the way down now on launches, so I could set it up to launch harder, I'd just have to make sure I didn't top it out or add a washer to limit the travel. It only got to about 47 on my 1/8ish mile test patch before I let off early. The brakes on this thing just don't inspire confidence at speed.

I haven't done any plug checks or anything else yet. I know it needs more tuning. I just hope it might finally be a setup I can work with.

[190mech]

Nice feeling to have a scoot that'll easily keep up with traffic!Glad all that heat up problem has gone away,I'm sure the knock left you too..After its run in a bit,time to fine tune it.Have you decided on a pipe yet??

[90GTVert]

I don't know for sure that all of the heat issues are gone, but they are certainly better. The knock has not been there with any cylinder but the 7,000+ mile, rod bearing failured, 54mm cylinder.

I'm considering getting another Leo Vince ZX. I gotta ride it with the fairings on to be sure, but it seems to fit well and it is working out pretty well. It's not really that loud... and I'm not really fooling anyone with a stock looking pipe. Besides, even the folks that may know a little about scooters will still see a fat guy on a little scoot and think nothing of it.

[2strokd]

:thumb: :drool:
MAn i wish you could come race it with me !!!
Glad its running good :cheers: :burnout: :twisted: