Big Bore Kit

[skishades]

I have a Super 8 150. Over the summer I was dealing with electrical goblins that kept blowing fuses and cutting out my lights. While I have done many things to my scoot, the problem lay in an untouched part of the system... Loose wire in the rear blinker (hate those intermittent problems). The not starting, hard starting, won't start problems were not just electrical though and my focus on electrical prevented me from checking mechanical. With the electrical all sorted, I checked my engine and found no oil and a point where it was seizing... The damage was done.

The simple fix, replace the scored cylinder, piston, crankshaft, bearings, gaskets etc... Basically, new top end... Of course I did some research and decided to make it more difficult and do a big bore kit. I had the engine machined out for a 180cc kit by Naraku, with a forged piston, new head and new cam (A8... Still using it for commuting, not racing). All the parts are Naraku. 

One problem, already solved was the big bore kit by Naraku needs a shorter chain (also by Naraku). The other problem I am running into, it seems to be a smaller head from the original which prevents the rockers from working with the cam... The old head really isn't designed for the big bore kit so going back isn't an option. The entire top end of my engine is now Naraku but I am not seeing recommended rocker arms, springs or replacements.

Anyone else done this mod and figured out the rocker arms?

FYI: The tolerances for the 180cc are extremely tight with absolutely no way for anything larger to go in. The shop machining out my engine to fit called me three times bcz of how close they were and they weren't sure they could finish. Definitely not for amateurs. I only did it bcz replacing the parts with new Kymco parts vs racing parts by Naraku was a few hundred dollars difference and I was already paying for labor. If I was doing it myself (too many other projects at the moment), I would still be spending a lot, doing the work and getting the exact same bike (labor would have been the real savings)... I just don't have the skills yet to do the big bore kit myself. But since I was hiring it out... I figured I would use their expertise to do what I cannot.

Update: The Naraku rocker arms fit the head perfectly. With that fix, the engine now turns over again... on to new problems below.

[skishades]

The new head on the cylinder changed the angle of the exhaust mount... now the existing exhaust won't mount and trying to find an after market exhaust to fit the Super 8 150 with a Naraku head is something else.

Any suggestions for new exhausts? I am going to a muffler shop that might be able to cut the exhaust mount and reweld it or make a new exhaust tube but none of that changes the muffler. Is the Yoshimura or Two brothers worth it? I want performance but still need to be relatively quiet in my neighborhood.

Also, I will need to change the ports on my carburetor for the new piston and exhaust. Can the ports be changed or should I plan on purchasing a new carburetor?  What is recommended?

Help is appreciated.

FYI: I am going to change the air intake... a simple change while I have it apart... to increase the air flow into the carb. All that is left is clutch, variators and rollers... Anything else?

[zombie]

That sounds like a very cool rebuild. You also handled the sticking points well.

For the exhaust you will find the same issue no matter what you buy. They will not line up.
I would go the route you chose, and have a shop cut, and weld your header pipe, and install any aftermarket muffler you like.

The Yoshi exhaust is classic. The tone is deep but not crazy loud. My brothers swore by them on street bikes. Crazy money tho... You could go the FleaBay route, and get one of those "performance" pipe/muffler kits for around 125.00. Then you would have a new header, and nothing really lost if you don't like the muffler.

For the carb jetting... I would go up to a 30mm fleabay carb. GY6, 30mm is about 60 bucks, and a handful of jets is around 20-25 bucks. The 30mm is probably so close that a needle adjustment, and air screw adjustment might just get it for you.

[skishades]

So you are recommending a new carb then and not just rejecting the original. Is there a difference in quality from fleabay to Naraku (they make a 24mm carb) and I have seen a 30mm molossi carb... A whole lot of fleabay though. Prices for "quality" brand is around 120ish. I was considering the Naraku bcz the whole top end is Naraku... But the Malossi is bigger...

As far as exhausts go, the two brothers is slightly lower pitch. I like it a little better for sound and I couldn't care less about how each looks as I would be happy with either look. My Kymco is yellow and blue and the power tip for the Two Brothers comes in gold... And I can get torx screws in blue continuing the theme a bit. It's stupid but I am way past that point with this build. The new header will be stainless but I will still need to have the bracket cut and rewelded.

This winter rebuild might be done in time for winter...

Since I have the top end mostly wrapped up, I will be doing the clutch, rollers and variator in winter. I see Malossi mentioned well in these forums. I need a quality brand. Is Malossi my best bet for quality?

[zombie]

Malossi is about the best for these scooters. Polini, and Stage^ are the same as Malossi. It depends on what you need the bike to do.

Nakaru is NOT up there in the list tho. They are the same as the generic China built parts. Just a fancy label, and an add budget. I'm not offending them or the parts, just sayin. Don't expect too much, and baby the engine. There not that strong for racing type builds. Malosi, and the others I mentioned are.

With the Nakaru kit I would stay on the budget end, and go with an Ebay carb...

Here's a 30mm for 40 bucks... http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X30mm+carb+scooter.TRS0&_nkw=30mm+carb+scooter&_sacat=0

Lots of us here have used these, and I have several that have lasted for years. If they ever fail? Get another.

[skishades]

I can't comment on Malossi or Polini since I haven't ordered any of their parts. The Naraku parts look nice and everything does fit... to itself. I went with a Naraku 30mm carburetor since I hadn't read your comment but I will remember that for next time. My impression of Naraku is they are built to be light weight so I know endurance will be an issue. Naraku made the big bore kit which is what set me on its path...

I looked at Naraku transmission parts against Malossi and Polini and I could really see the build differences and was the first time I began to question the quality. Naraku wanted to add 2k rpms to engage the clutch and everything looked thin in the pictures of the others. I can't imagine my engine lasting very long with a Naraku clutch. It seemed really great way to get really high power for a short amount of time... not at all what I am after. I just want the reserve power to be there in a pinch but I want to trust I will get to work or finish the ride.

Sadly, the Two Brothers Racing exhaust is no longer made and completely unavailable... despite what websites are claiming. The only after market pipe left was Yoshi (purchased the carbon solely bcz of the weight difference). The difference, a slightly louder, higher pitch exhaust. I really liked the lower rumblings of the TBR though and it had a sound reducer to add too... oh well.

I don't want to tax the engine too much so I am looking for a good clutch. Malossi is $180, Polini $120 and Naraku is $110 (but it revs high by design which means its not an option for me). Already purchased a Naraku Variator with 11.5g rollers (and 9.5g rollers for those wanting faster starts). I will probably need to add heavier weights but its a starting point. All of this is new to me. The transmission is my winter project... I really just want to get this bike on the road for the summer and carefully pick the parts out for the transmission so I am ready when its time or if it breaks.

My mechanic is trying to convince me to replace everything now but want to do the transmission myself. He also is concerned my starter can't do the higher compression, the clutch won't handle the extra power and that my belt will explode. My starter motor is the same as the ones in the Kymco 200i, which is a 180cc moter... so it should be fine. The clutch and belt should last through the summer and if they don't, I really want to do the work myself (I just barely knew enough to not attempt the engine bore myself... but I do think I can do the transmission).

Do I need to replace the pulley? or any other parts of the transmission?

[zombie]

Don't worry about your mechanic. He's comparing a big block Chevy to a golf cart engine.
In premise he's right but in application... not so much.

Go to Racing Planet, and open a dealer account. "Joes Scooters" or whatever. for the tax ID just use your Social, and pay the sales tax. Mechanical parts ar around 40% off retail.

Get the Polini or Malossi clutch, and set it u the way you like.
Don't worry about the belt or the pulleys. They are more an fine.

[BettinANDlosing]

Don't worry about your mechanic. He's comparing a big block Chevy to a golf cart engine.
In premise he's right but in application... not so much.

Go to Racing Planet, and open a dealer account. "Joes Scooters" or whatever. for the tax ID just use your Social, and pay the sales tax. Mechanical parts ar around 40% off retail.

Get the Polini or Malossi clutch, and set it u the way you like.
Don't worry about the belt or the pulleys. They are more an fine.

When I signed up for a Wholesale at RacingPlanet they needed pics of our shop, but that would be easy to fake I guess. They are a bunch of Russians anyway.

[skishades]

Well, I have an update. Scooter runs, I am breaking it in at 40mph for the first 300 miles... definitely has pep. I am learning to jet and adjust the carb a bit at a time. I have not touched the original 60 idle jet nor have I touched the needle. I have changed the main jet from 138, which bogged past idle to a 120 which bogged and popped past idle. My 130 came in last week and I have power... still bogs at the transition between idle and the main. After 120 miles, I checked the plug and found the tip white and the ring black and forums are suggesting it is about right (though a lot of pictures and descriptions would disagree). The ceramics are intact and the metal does not look dented/pitted.  I think 128 might be the ticket but also thought adjust the AF might work too... if it has one. There is no clearly marked screw for the AF.

[skishades]

Is that a cover on the AF?

[skishades]

The new carb bottom needed a new carb manifold which did not sit as high as the original manifold reducing the clearance for the carburetor. The carb bottom has that protrusion for the drain which stuck out too far. I took the old carb bottom off from the previous carb and it fits perfectly. Carb sits tightly against the frame of the bike but it works. I also used a radiator hose to fit the new air filter on and S it around where the filter would fit, around the same place as the original air box. Drilled holes and connected the vacuum lines into the radiator hose and everything now works. The air filter is 50mm and originally would be knocked off by the seat pan due to its size. The new location just makes it easier to clean or change in the future.

[skishades]

With a large top case by GIVI. I ride at night so my pics are at night  . You can see the air filter and the missing air box in the photo. Too bad you can't hear the sound!

[skishades]

Still breaking in the motor but the first tank of fuel has was used up and I averaged 70mpg at 30'ish mph with the upgraded engine. The second tank, I remembered to put premium fuel in instead of regular and it made a huge difference. I had A LOT MORE POWER! After I used up a tank of premium, I averaged 88 mpg at 35-40 mph. I am slowly breaking in the engine and I am working on the last 100 miles. I plan to change the oil at 300 and see how the new parts are holding up. So far, I am impressed.

[Amaro321]

How is this working for you


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