Chainlube
Well-Known Member
Only change the width of the intake and exhaust ports, or you'll make a nice paper weight.
100cc or 80cc which one?
- Thread starter Ivan168
- Start date
Today I took the cylinder off and ported it, I filed the intake and exhaust but that actually made it worse, now I've almost lost the low end, I don't know why, I haven't touched the transfer ports, the carb is the original one, I tried a copper gasket but it still runs bad, soon i had ported another cylinder to a friend and the effect was noticeable towards the bottom end and now here it is gone, maybe i opened these holes too much and i don't know what to do, i wonder if i should put glue and then grind the holes?
D
Deleted member 9837
Guest
If you mean to glue with JB Weld or something similar, I say NO. If you ground off on the top or bottom of the ports you may have a permanent problem. I wonder if using a thinner case to cylinder gasket may help, or even grind down that mating surface which could lower ports. Taller piston?
Unfortunately I've been reading of more and more ruined cylinders from attempted porting. I think manifold matching, a little polishing, and smoothing the edges of the ports to keep the rings from hanging up are as much as I'd attempt..
Unfortunately I've been reading of more and more ruined cylinders from attempted porting. I think manifold matching, a little polishing, and smoothing the edges of the ports to keep the rings from hanging up are as much as I'd attempt..
I already tried with JB Weld and the result was expected, the glue does not withstand the temperature and pressure of the exhaust gases in the exhaust port, only in the intake port the glue holds but overall it did not improve, I just needed a new cylinder, unfortunately exactly that's what i did, i blind filed a lot of the top and bottom of the ports and that literally killed almost all the power and the cylinder was junk, unfortunately a lot of people mislead on this subject by saying it's fine to file the ports as much as you want and it can destroy more cylinders of other people (as I was) who don't know what they are doing, such claims are most often found in the reddit group, honestly I would advise people who are not sure what to do, just smooth the edges of the ports without touching anymore , that's the least of the evils, the original ports do not work well, but if they are ported incorrectly, the engine will work even worse.
Using a thinner gasket to the case and cylinder might help but it's unlikely to solve the problem, same goes for a taller piston, if the ports are widened incorrectly the only solution is a new cylinder, to be honest I didn't think porting was that complicated either, but it turned out to be a whole science, and I personally wouldn't touch more than slightly widening the intake and exhaust ports and smoothing the edges, after replacing my cylinder with a new one, I widened the ports by 1mm on the sides, smoothed the edges, scraped the head and cylinder by 1mm and I made a brass gasket for the 0.8mm head, currently the compression is 140-150psi, which is the maximum for a long engine life, this increased the low and high end, and the work in the middle end is very pleasant, but I think that you can't ask for more from a stock 80cc .
Hi again, so far the engine is running fine but I used it's carb on another bike, and now I have to dig a new one, and I was wondering if it's worth buying a speed carb that they say is big o or an HT carb, will there be a difference in power after porting?
Gordy
Well-Known Member
Just get another BoFeng.
Agreed. Here is a link for the JRL BoFeng, I have used them for years and am quite happy with them and their performance....A great carby for very little money, only $11.99 USD...lol.
This is the USA amazon URL link...You will have to see if you have a URL link that covers Bulgaria.
https://www.amazon.com/JRL-Carburetor-Stroke-Motorized-Bicycle/dp/B08N9WYS1V
Links to Amazon may include affiliate code. If you click on an Amazon link and make a purchase, this forum may earn a small commission.
So you are saying to get the Baofeng again which was actually the original with the kits, I am asking because I am being offered the so called "speed" carburettor for the same price but I am reading mixed reviews about it, some say it will improve performance but others say it may make it worse.
Here's one in question: https://gasbike.net/products/speed-carburetor
Here's one in question: https://gasbike.net/products/speed-carburetor
Gordy
Well-Known Member
That NT speed carb is nothing but problems. The BoFeng is actually an upgrade from that.
