Couple Question's

Inky

New Member
Jul 27, 2013
11
0
0
27
Arizona
So im not all that experienced with aftermarket parts, performance, power, all that. ive always built these things stock but i decided to go all out this time and i had a few questions im sure you all can answer with ease;

1) Can I run a stock engine with a HP carb and HP expansion chamber without messing it up or do I need to upgrade the rest of the engine to match?

-I plan on upgrading almost everything but cant afford to keep dumping big chunks of my paychecks into it so progress from here will be slow and id like to ride in the meantime if possible.

-I ran the engine stock long enough to break her in good n' proper, then stripped everything but the frame and wheels for a friends bike so i could build this one from the ground up.

2) How long will stock tires hold up under a more powerful bike? Ive gotten a flat on a different bike going about 25 and it was not a pleasant experience and id like to avoid it happening again ;]


I do plan on upgrading the entire engine with a high comp head, jag cdi, all that good stuff, as well as some good tires, rims, maybe even a jackshaft (those things sound awesome!) i just need to know if once my seat and brakes come if i can ride it to work without worry of ruining my first in depth build before its even done.

Thanks Guys!
heres some pics, red is what it looked like originally when i had it running stock, bare frame is after stripping parts and painting, obviously black and chrome is my unfinished baby :3 remember its a work in progress and excuse my messy apt ;)
 

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wheelbender6

Well-Known Member
Sep 4, 2008
4,011
135
63
TX
Most any engine can handle upgraded intake and exhaust without any internal changes. Internal engine changes are usually needed when you rev the engine much higher than stock. You increase the rpm range on a 2 stroke with porting mods. Four strokes generally require a bigger cam to increase rpm capability.
 

ivan H

Member
Oct 8, 2011
622
1
16
australia
Hi, as ur planning on increasing compression, I would recommend changing the small end bearing (piston wrist pin bearing) to a wider & better quality item (if u have a 66cc). The stock bearing is a low quality 10x14x13 that drifts axially on the gudgeon as the bosses in the piston can be up to 16 or 17mm apart, thus the bearing can drift like, half outta the rod almost. Replace it with a quality 10x14x15 bearing, or if u can get one, a 10x14x16. I think NTN make a 10x14x16. If u check on Jags site I think he says to do this bearing change if increasing compression. Its recommended many times on this forum also. Hope this helps. Cheers
 

Inky

New Member
Jul 27, 2013
11
0
0
27
Arizona
Thanks for the replies!
Chainmaker that guide helped a lot, thank you good sir.

Ivan where might I find a good guide for changing the bearing? i had no idea that i would need to replace that thing. and dont know how
 

ivan H

Member
Oct 8, 2011
622
1
16
australia
Hi,I'm not sure where u'd find a guide on changing that bearing but it's pretty easy. The good folk here would talk u thru it. Remove the head & slide the cylinder off. Now stuff a clean rag down into the cases so nothing can accidentally get dropped in there, or anything for that matter. Now u need to remove one of the circlips that keep the gudgeon pin in place. A pair of long nose pliers will do for this. The clips r shaped like an "e", so look at it & work out which way to twist it to compress it. Take ur time & be carefull not to scratch the piston. Remove the clip from one side & u can push the pin thru from the other with the circlip still in. With the pin out the piston will lift off & the bearing can be slid out of the rod, the new one placed in & the piston put back on. It must go back on in the same orientation as it was before. Marked on the crown (top) is an arrow that must point toward the exhaust port, or front of the motor. It'll be easiest if u have the pin already in the side of the piston, just a tad past the boss so u can locate it in the bearing & slip it home. Replace the circlip. Before u slide the cylinder on, notice in each ring groove there is a pin to locate the ring ends. This is to keep the ring ends out of ports. They,ll be at the back of the piston, (either side of the intake port). Make sure the rings r located properly & then use ur fingers to squeeze the rings into the grooves (compress them) while u slide the cylinder on. From there u should be right, u only need to torque ur head up. Its a good idea to replace the 4 acorn type head nuts with decent quality nuts & use flat washers. Also, replace the fasteners that mount the motor to ur frame with high tensile ones. The junk ones that come with these Chinagirls are notorious for breaking. Cheers
 
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