70cc kit

[hazza]

Hi, I have a CPI Oliver 50cc and I have put a Leo Vince TT exhaust on it. I changed the rollers for the ones that came with the exhaust (3.5g) and it is OK at best, I also up jetted from the stock 47.5 main jet to a 60 which helped as it was bogging really bad.

It has a Mikuni carb which is the stock one.

I would like to install a 70cc kit and have been watching one on Ebay from Taiwan which you all seem to like.

My questions are, will the Leo Vince still be OK and will I need to change the rollers? Also will I need to get a new carb or can I upjet the one that is on? It takes Dellorto 6mm jets so no problem getting hold of them. It also still has the stock air box.

Any help would be much appreciated.

Thanks

Harry

[reveeen]

will the Leo Vince still be OK?

Yes, and no...... it will work, but not as good a a pipe designed for 70cc. You also do not say if your pipe is "de-restricted", or not. If not de-restricted now would be a good time....though it WILL mess with your carb jetting.

will I need to change the rollers?

Again: yes, and no.... many times when increasing the displacement you will find the drive belt slips, this means a stronger spring in the take-up (rear) pulley, requiring heavier rollers if you wish it to behave as before.

will I need to get a new carb or can I upjet the one that is on?

Either: Increasing the engine displacement changes your fuel mixture ratio, so expect to have to re-jet, or for maximum benefit: increase the carb size.

I *guess*, at the end of the day, the bottom line is money, and what you can/wish to afford.

[hazza]

Thanks for the reply reveeen.
The exhaust is derestricted (washer removed) and I put in the rollers that came with it and also the 3 stronger clutch springs. I guess that heavier rollers will be needed but the BBK comes with 3 different weights so should be OK on that one. I maybe will need to change the contra spring for a 1000 or 1500 but that shouldn't be a problem.

I would rather not have to buy a new carb if I can get the thing running reasonably well with new jets, but if I need to I will. I suppose I will have to try it and see how it goes.

Thanks again
Harry

[90GTVert]

If you order the kit from Autotech355, he sells springs cheap too. You can email him and maybe just pick up one contra spring if you don't wanna buy a whole set. Not sure if he sells em separate, but it might be worth a try.

The stock carb, especially the Mikuni, should be OK. Not ideal, but it works fine with sport kits (like the one you are interested in) when properly tuned. A Dellorto 19-21mm would be my choice if upgrading carbs with that setup. They're great little carbs. That's $100 or more by the time you get jets and such that you don't really need to spend right now though.

[hazza]

Thanks 90GTVert, that is the one that I am looking at on ebay $110. I will drop him an email re the spring and see what he says. Which spring would you recommend?

If the stock carb runs Ok I will leave it on untill I can get another at a reasonable price.

I'm not looking to blow anyone away, I just want a bit better performance.

Thanks guys
Harry

[90GTVert]

I think you'll probably be fine with stock, but I'd say 1,000RPM contra if you pick one up just in case.

[hazza]

OK, kit is on its way and also a contra spring, hopefully they will be here by the weekend.
I guess that the rollers will need to be changed for some slightly heavier ones as the ones in it now are only 3.5g. I have some 4.5s and the kit comes with 3 other weights. What would you recommend. It comes with 5, 6 and 7g weights.
Also will this carb fit? looks like a bargain to me but doesn't say what mke it is or jet sizes.

cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=190533823905&ssPageName=STRK:MEWAX:IT

Thanks
Harry

[90GTVert]

That carb will fit, but it's just a stock carb that they've labeled 19mm because they don't know how to measure it. lol If you measure most stock carbs at the outlet, they're 19mm. At the venturi most are about 14mm.

Honestly I'd just leave the CVT alone. You should know pretty quick if the weights are too light. The way it feels should give you some idea of just how much heavier to go. Some people will just install heavy weights at first to keep revs down for break in. I don't, but I can't say it's a bad idea either. Just a guess on roller weights would be 4-5 grams, so I'd start off with 4.5g if you really wanna swap 'em pre-ride. If you use the contra spring you'll need even heavier rollers.

[hazza]

Thanks for that Brent, I'll see how we go with 4.5grollers and then take it from there.

I don't really want to buy a new carb but the one that I have now is looking a bit bad.
If I turn the air screw more than half a turn out it stalls so it is set at just a tad below half a turn. I'm not sure if the guy who had it before me was a bit heavy handed and has tightened it a bit too much at some point.

Thanks again
Harry

[90GTVert]

That's how the carb I have on Project 90 is now. As long as you are able to adjsut it for a good idle, I wouldn't go out and buy a new carb. If you do buy a new carb, you might wanna consider something that's truly in the 17.5 - 21mm range so you might pick up some performance for the money you are spending. The aftermarket stuff is a little more adjustable too in most cases. You can get different needles and atomizers and stuff like that if you so desire. Some allow for quick jet changes. Good stuff.

[hazza]

Thanks Brent, I may just leave it and see how I go with it.
Another question for you. The speedo on the CPI only goes to 50MPH and it hits the stops already (very optimistic)
Would a speedo from an Oliver 125 be a straight fit or will I need to change the drive gear etc.? It is identical in fit and looks but the reading is higher.

Cheers
Harry

[90GTVert]

I really don't know. I never put much effort into the stock speedos. I have Sigma bicycle speedometers on all of my scoots. When calibrated properly I can bring along my GPS and watch the speeds and distance traveled match up. Pretty cool for something you can pick up on ebay for somewhere in the neighborhood of $20.

49ccscoot.proboards.com/index.cgi?board=instrumental&action=display&thread=395