DIY guy went HT Motorized Bicycle

[Agreen]

Re: DIY guy went HT

Pics are hard to get in the light, but I think a couple of them show the signs of scoring and some of the pits. Really, there's nothing in there that is enough to feel, so I probably shouldn't be worried about it too bad I guess. Can't even snag a fingernail over any of it.

How about some 1000 or 2000 grit sandpaper to polish things up? That wouldn't flake it off like the hone would, right?

 

[Theon]

Re: DIY guy went HT

All I can say is it may have been wise to strip the motor before running to remove metal fillings and Chinese soil.
I have just ordered a new motor kit from Ebay.
I did not go with the cheapest, nor the most expensive ($169 Delivered).
The deciding factors were centre fire head but more importantly 40mm stroke!
It may take a week to get here as I'm a little remote, and can't guarantee metal filings in the motor but I will be disassembling it from new and I should make a thread of it.
I'm tempted to get the crank balanced while I'm at it.
But will likely run the motor first to see if its necessary.
I will be doing a full port job on it from the start, as well as lightening the piston, and reshaping the head.

 

[Agreen]

Re: DIY guy went HT

I chose mine based on a few selection criteria:
-They're all from China, so you're taking a gamble no matter what. So I wasn't going to spend a lot of money.
-Roller bearings > bushings. Car engines use regular bushing style bearings, but they have things like oil pumps that forcefully lubricate them.
-I wanted the slant fire head since I knew I was dealing with some tight spaces on my particular mountain bike frame.


I think I'll just try cleaning up the ports, polishing the cylinder walls, and seeing where that gets me.

 

[Theon]

Re: DIY guy went HT

Yes I will be disappointed if it comes with bushes, But I plan to make this one a slow rev'er. It's going to be the new motor for my Softtail, so have a shift kit and I already have two 9000+ RPM motors.
This one I'd like to get as much low to mid as possible, hence the 40mm stroke for max torque. And a bushed crank may be better for the reasonably high compression I plan to run.

 

[Agreen]

Re: DIY guy went HT

Man, I don't know how you guys are able to get in to the transfer ports to smooth those things out! I couldn't get any tool I know of in there...

I went ahead and smoothed out the intake and exhaust ports though, re-shaped the one that was kind of off-set, made it more of a rounded off rectangle, and polished up the inside with some 1000 and wet 2000 grit sandpaper. I didn't have a new head gasket, so I tried to anneal the one I had. That ended poorly, as I melted right through it with a regular plumber's torch. So I bought a mirror and lapped the head and jug a little bit with some 200, 400, and 500 grit, then laid a thin layer of copper sealant down and torqued the head on without a gasket for now. Amazingly, there seems to be NO sign of leakage whatsoever, as opposed to using the original head gasket. The torque is significantly higher than before (obviously, with the higher compression ratio and all). I'm noticing that there seems to be a limit on my rpm though. I'm thinking it's ignition related, so I ordered a decent NGK B5HS spark plug, a new wire from sickbikeparts.com, and a new head gasket... just in case I want to go back to a gasket. For now, the sealant is working wonderfully, so we'll see how far that gets me.

I'm also thinking of changing frames. I have an older huffy mountain bike that was my testing guinea pig of sorts, so I'll be chopping off all the welded on accessories that I put on it, smoothing it all out, and re-painting it. I'll probably swap the wheels and brakes from the schwinn over, since they're much higher quality, and then swap the engine kit over as well. The new frame will offer more space, so I won't have to have a carb hanging out the side, and there is more space on the rear stays, so I won't have any more rubbing issues. Another plus is that I won't have to remove the whole engine to remove the cylinder head. I should have realized just how tiny the inside of the schwinn's frame is!

 

[Theon]

Re: DIY guy went HT

Your main Jet may need to be a little smaller, that could be holding back your revs?

 

[Agreen]

Re: DIY guy went HT

Made a new intake manifold for it today. The quality of metal is not very good, so I was having a rough time getting a decent bead on it, but it seals at least. As I go to put the carb on with a new O-ring, one of those little aluminum tabs broke right off at the base of the carb, rendering it now completely useless. So now I have to wait until next week to get another one in. I guess it could be worse. I could be in AUS and have to wait a month for it

 

[Agreen]

Re: DIY guy went HT

So I only waited a week for the carburetor, but that was too long to not work on the bike, so upgrades were inevitable. I ordered a new plug wire and spark plug from sickbikeparts.com, along with a dual pull brake lever and a head gasket. The gasket is still not installed, since I'll only be installing it if it shows signs of leakage.

I installed the new carb (same NT as before) and sealed it off with an oring. I also installed the spark plug and wire. This thing rips now. I'm satisfied

 

[Theon]

Re: DIY guy went HT

Good stuff, I've never tried to run any of my motors straight out of the box, they've all needed something done to them first, but there that simple, and I find them fun and cheap to play with, a rewarding hobby.

 

[Agreen]

Re: DIY guy went HT

I feel like I should have seen it coming, and I really wish I had taken the engine apart before running it. I think I could have prevented the cylinder wall scoring and pitting, but if it dies it dies, and I'll rebuild.

I have a feeling that the engine runs a lot better with a properly sealed carb and he decent ngk plug and wire aiding the spark in there. There is no more rev cut, so something I did had to have fixed it.