Here's what I did in addition to some of the stuff already mentioned. I widened my exhaust port as far as I safely could. I smoothed out the crude cut/bend in the intake tube. I made a larger longer headpipe and gutted the stock muffler (looks like a poo poo pipe now). I run the chain tensioner on the peddle chain side for 2 reasons; the first being safety and I gained about 3 mph by doing so. I jetted down one size prior to making the pipe and it took almost all of the 4 stroking away which it did badly. I run a 40tooth sprocket and it will still pull me up all but the steepest hills and cruises nicely at 28-32mph. Top speed on the bike computer was 42mph before the pipe mod but it was wrung out tight. I didn't get more than a half mile on the pipe before snow came. The acceleration was tremendously better but I don't think it helped top end and may have even hurt it. Maybe it needed more main jet I don't know but I was after low end power so it doesn't matter. I'm not chasing speed I want ridability and dependability
cheap 66cc engine mods
- Thread starter bradentonmotorbikes
- Start date
i have a 27t on a 20in rim (chopper) and yes i do have to pedal more before releasing the clutch and it basically will only accelerate once i have hit top pedaling speed but it is way faster and i am thinking about going with a 20t......perhaps even 16t...i cant wait to get a speedometer...
I do hope you know that the smaller sprocket won't give you any less speed but will hurt your acceleration some more.
best cheap mod on my bike was to add generator 24 bucks the other was adding a charger 24 bucks and battery pack 10 bucks runs lights no draw on cdi.
You can try a home made double sealed expansion chamber or get a bigger port intake so the engine can get more gas
what i dont understand is why would you want to go over 40mph on a bike anyways? unless you have a nice beefy frame and wheels and your on a race track whats the point? LOL! I live in mexico now and they very rarely use signals and have tailights that work, so im good going slower( and im retired and dont really have to be anywhere fast)!! LOL
Watch out for that vintage style analog speedometer that I see a lot of people selling for about $10. Well, when mine was telling me I was going 55 MPH, I started to get a little suspicious. Yes, I do have a very fast bike: I have a custom 30 tooth sprocket, I weigh about 190 pounds, and nicely tuned engine with an expansion chamber and a few other things I probably can't mention (no nitrous) If you want to know, you'll have to ask me outside of this forum, but 55? Really? I don't think so, so I went to Walmart and bought a Schwinn digital speedometer. You can program you exact wheel size; my bike has a 26 inch wheel, with medium sized tires. Well, what was the final verdict on how fast I was really going? On a good day, I can reach 40 MPH on the flat, which is when I believe the CDI stops the engine from revving higher.
That is about as accurate as I can be, honestly.
That is about as accurate as I can be, honestly.
When you say cheap mods, I thought, hmm, these things usually cost a bit, but I thought of one interesting mod.... I wouldn't be surprised if some of you have already tried it, and it's probably old history to you guys, but here it is: Take the head and cylinder off and remove the gasket which seals the cylinder to the case. In order to maintain a good seal, I like to use the anaerobic gasket maker because it's the best quality and won't let you down. It's a little scary of a mod, but I've done it, and for me, the piston did not hit the head. When I did it to the stock head, boy that engine really put out a noticeable increase in power, but once the engine started getting hot, it started to detonate, so I had to back off and let the engine cool down. Later, I took a little die grinder and relieved some of the material where the spark plug threads end (slant head) in the combustion chamber. The threads don't do anything except possibly get really hot because they are sharp, so relieving them is a good thing, but don't do too much, cause you will lose the compression gain you were originally trying to attain. If you don't have high flow intake and exhaust, you may not have to do any relieving in the head. I've only tried this with a slant head model. Oh, another thing about the slant head: I like to orient the head so that the spark plug is on the intake side of the engine. This is because when you relieve those jagged threads it will mainly be on one side. This will guide combustion activity to be offset slightly, favoring the intake side of the piston. I believe this is beneficial because the front side of the piston operates at a higher temperature because it is in close communication with the exhaust, and keeping the intense heat a bit towards the intake side helps even out the piston temps. This is a little risky of a mod: My crankshaft is straight (CR Machine reworked engine), and that actually makes a slight difference in the length of stroke for the engine, and therefore would affect the compression (it lowers it). All the cranks I've seen are bent in the same way; they are essentially bent in a way that actually increases the stroke (and compression) of the engine! I know it seems F'd up, but it's true. When I saw how distorted and misaligned the cranks were, I started tearing down every new engine I get and reworking them. Sorry this is such a long post, but just because I didn't have the piston hitting the head, doesn't mean you won't if you try the mod, because unless the engine is one of my reworks, it probably has a bent/misaligned crankshaft.
Hope you found this information helpful or interesting or both. Thanks
Hope you found this information helpful or interesting or both. Thanks
