Tuning a B1 China replica

thats funny you mentioned that. last week i was thinking the same thing. I used both on my Gem. the result was what I expected. i had great acceleration through out the whole rpms.I'll know more when i take it to the track tomorrow.

yesterday i decided to work on my c1. it never ran right from the beginning. but now it runs like a champ. what i did was shave off 1.2mm of the top of the barrel from 57.2mm to 56mm from top to bottom. then used the old head gasket. there was 2 stuck together. one was 1mm thick and the other .5mm thick. i ended up using the .5mm and a light film of copper gasket maker.

while i had the head out i cleaned up the water jackets. one side of the water jacket was totally clogged up so i drilled it out and hit it with a dremel.

also the ports were so mismatched, i ended up match porting all the intake ports. the gaskets were overhanging so i trimmed them back too.

i got the head back on and the squish is set to .65 right now and i can go lower by using a thinner hg gasket now. (.4mm gasket would bring it down to .55mm) I also switched out the plug to a NGK B9EGV racing plug.

next i swapped out my carb with a dellorto 14 with a 72 jet.

i already put a polini clutch in there with a blata drum and 7t polini pinion.

the results are great.it use to have a huge lag in acceleration from low compression but thats all gone. the jetting problems are all fixed with del carb and jets. the clutch problems fixed and so far no cooling isuues. it revs like a mo fo. compare to my real B1 it comes close but i think to get it to its full potential it would need a stuff race crank, new bearings,seals, match port the case to barrel, a 17.5 or 19mm carb,reed spacer and a new race pipe.

next i'll be figuring out how to get this bike to handle better. i have a damper, i just need to weld a tab on the frame. i want to redesign the swing arm to be adjustable.
JSIGONE thats wher i need your help with that program.i'll give you a buzz and you can fix that barrel tonight and grab that jet.

Yah I'll try to come over around 7 or so, after traffic dies down a bit. I need to take the head off the bike still. I was too lazy to do it last night

I'm waiting for a software upgrade that allows me to do wire haresses better in solidworks, it also has a tube bender program as part of the feature. I've already mocked up the center alum braces from the C1, jus need to dial in some of the measurements and draw in the stock swing arm. That way I can visually see the difference in the new design. I have a few ideas on how we can get it to do what I want it to. I'm not sure how u want to lower the seat but it CAN be done I'll go over that w/ u.

Well guys I've been busy doing a little wrenching on my C1. I pulled the motor and split the cases. My ports were also waayy off. I gasket matched the cylinder and cases. I ordered ALL new water pump parts from Tom @DCminimoto from the pulley to the impeller.......also ordered the gaskets and a Blata W/P belt. I've got all the parts cleaned, lubed and ready to go once the Blata parts arrive(C'mooooon... Tom ). I also just placed my order to MidSouth for a 14-14 Dellorto ( Thanks Jsigone!!) and 70-72 jets. I'm also putting together the coolant fan setup(thermostaticly controlled).

On a side note-- I finally got the PBU Headstrong kit on and nearly tuned. Heading out tonight to a wider open testing spot.

Loves to turn me some wrenches!!!!!

Banzai !!!!!!!!!!!

Can one of you guys pls take pics of the Squish thing i really dont understand it.

squish is the gap between the egde of the piston and the top of the head (head cap is what I call it) Remove the spark plug, stick a piece of solder in there, make sure it touches the edge, pull the pull starter til it hits and squished the solder, then measure.

Why do they have two head gaskets??? LOL

Where can we buy gaskets of different thicknesses for tuning purposes?

Got a better image in my mind now thanx

i sanded the head down earlier, still putting the bike back together w/ locktite and RTV in the needed places. Old squish was 1.8mm w/o a HG and new squish is .45mm w/ the stock .5mm gasket (there was two gaskets, one thinner, I used that one).

I got to hear Rex's bike, sounds **** good, no hesitation now.

Can you give a thorough explanation as to how you went about milling the head down? What surface(s) did you mill, and how did you know exactly how much material to remove? How did you keep it all perfectly flat? thanks.

I machined the top of the head cylinder. My squish was 1.80mm
Machine 1.3mm off
leaving a squish of .50mm

Went from 56.9mm head to 55.6mm

Once u know the squish, u can determine how much to shave off

So yours was initially so low (compression ratio) that the piston wouldn't even touch the solder when cranked? So how did you determine at that point how far the piston was away from the underside of the head at TDC?

i removed the stock HG, got my squish and went from there

Do you guys get any problems with pinging / detonation after you increase the compression? What octane gas do you use?

knowing that the squish on blata B1 are set at .35 to .5mm and it didnt register on the solder. we knew it was more than the thickness of the solder which was 2mm.

measure the thickness of your gaskets because they might be both different.i had 2 and one was 1mm and the other was .5mm

no i had no pinging. the compression is at what its suppose to be anyway.i also use 101 FnL racingfuel which has a motor octane of 96.

REMEMBER GUYS WHEN DOING THE SQUISH BAND TEST, PLACE THE SOLDER TOWARDS THE END OF THE WRIST PINS (SIDES OF THE ENGINE)BECAUSE YOU COULD GET FALSE READINGS DUE TO THE PISTON SLACK.

I'm using VP110 so it doesn't ping worth a **** runs a lil rich so I have to run bit leaner then others do to make good use from the race gas. All bout tuning and trying differnt setups til u get it dialed in.

I was speaking with a racing snowmobile tuner today. He said for high strung 2 stroke engines that have a high rpm clutch engagement, a good way to make power is timing advance. He said to do this double gasket between barrel and crankcase, and mill the head a corresponding amount, thus moving the ports up in the cylinder. Anyone lend any validity to this?