- 2STROKE STUFFING
All I would like to know is: 'does this really work?'. I would love to hear some thought and advice.
Thanks.
Base Spacer
- Thread starter Chad_Broski
- Start date
All I would like to know is: 'does this really work?'. I would love to hear some thought and advice.
Thanks.
I would also like to know 'if it does work, what adjustment will I have to make to maximize efficiency/power gain (besides porting, which I am already aware that I will have to do that eventually)?'
If you add a spacer to raise the ports you have to deck the cylinder the same amount to get the compression back to where it was, you’ll also need to check the piston skirt at the intake port at top dead center to see if you need to trim the piston.
Remember that raising the ports will help top end but will hurt low end, I have a 49mm bore engine that runs great at the top but is weak at low speeds.
Also look for Graham Bells book on two strokes, i downloaded both and use them when porting. A lot is way over my head but it gives you a working knowledge of the process.
Fascinating
Also, just wondering, if "raising the ports will help top end but will hurt low end", then is the reverse true also? As in if I lower the ports, will it help low end but will hurt top end? I am not really that worried about top speeds RN, I preferably just want low end torque. If you can answer this I will have one last question. Thanks for the recommendations!
You can try rtv instead of the base gasket, you’ll need to check the squish clearance to make sure the piston has enough clearance.
I have found a work around of sort with a expansion chamber, I went by the books above to set the port timing on a grubee 48cc, then added the chamber and a silencer to help control back pressure. I got improvement in top end and bottom end torque. I have 128 degrees of transfer duration which Graham says will produce 8000-9000 rpm, I’ve got 8200+ from mine.
Be careful when porting transfers, they have to match. If you get them wrong it will hurt performance.
Also, thanks for recommending this manual
Jennings: Two-Stroke Tuner's Handbook
Awesome, what are the specs?
I would share mine but it's just bone stock (nothing special), and it sputters lots of oil all over the engine and bike frame, and since it's so dusty where I live, the bike has shifted colors from a matte black to a light brown, lol.
I would share mine but it's just bone stock (nothing special), and it sputters lots of oil all over the engine and bike frame, and since it's so dusty where I live, the bike has shifted colors from a matte black to a light brown, lol.
Wow, now I have so much more questions. First off, what is the average connecting rod length of the standard cheap china 2 stroke "80cc" engine? Are the rod length's universally the same for all these off-brand models? I am trying to find the maximum piston acceleration that the piston rings can handle by using this equation: G max = (N2*L/2189)*(1+1/2A). But I need A, which is "the ratio of connecting rod length, between centers, to stroke" but I don't know the rod's length. Also what are the piston ring sizes and do they vary from kit to kit, or no?
All I go by is which piston the engine uses, type A is a low pin piston, the pin is located 15/16 up from the bottom. Type B or high pin piston has the pin at 1-1/6 up. The rings are 47mm on a standard engine, I buy rings in bulk, usually five sets at a time. I have a 66cc 38mm stroke and a 69cc 40mm stroke and both take the same piston. If you’re replacing a piston you need to measure to see what you need.
My 49mm bore engine is a 75cc, it was a 47mm bore 69cc. I got the iron sleeve piston and cylinder from eBay.
Okay, guess I will have to take apart the engine to measure the connecting rod,
Same as mine.
That seems to be very useful, where did you find it at, or did you have it printed off?This is how I check port timing.
I printed the wheel and glued it to a dvd, it is accurate enough for what I’m doing. Both of mine use the type B piston, the 40mm stroke I converted to the 49mm iron sleeve.
