Metrakit 2, no power whats upt?

[StepVino]

Yes that is deck cleasance.

I get same number ~192. If I add 0.7mm base gasket, I get
to 11k. Wouldn't take those numbers as sacred though, it might
be fine just like it is.

 

[adas]

Aloha, OK I got the "balls on" accurate measurements now

42mm stroke
.50mm Deck (includes base gasket)
23.0mm PortTop to BarrelTop

I get 9300 to 9700 rpm power range. This is low, but I want it low like this for quieter around town driving. But it is a bit low for the C16 @11,000 so I have a couple of longer flanges that bolt onto the cylinder made that fit into the slip-joint.

Does anyone have a program to show pipe length vs rpm?

thanks
Frank

 

[adas]

Aloha, OK now I am in the ball park. I have a power band!! Have a lot of tweaking to do, rollers, carb, possible air leak. Here is where i am at

1: .25mm base gasket, 2mm machined off the base (using a stroker 42mm crank) This setup has the piston top on the bottom of the exhaust port at BDC. And the piston comes right to the top of the cylinder, less .25mm deck

2: Using a Malossi head I get .57mm squish.

Power starts around 9000 rpm. (I will lengthen the C16 pipe 2 inches later to match the pipe closer to the rpm of the to cylinder)

3: Now I have a lot of rattling (detonation?) or extreemly lean. Did someone say it was necessary to retard the ignition?

4: when hot the motor may rev up like crazy 7000rpm with no throttle, but I can fine no air leak. Will double check as there MUST be an air leak!!! Or maybe I am just way too lean?

But power hits considerably better than my Malossi Replica.


Frank

 

[StepVino]

Congratulations! Hope you get the small leftover tweeks
sorted out soon. I guess the Polini head hits the piston?

 

[narx]

3: Now I have a lot of rattling (detonation?) or extreemly lean. Did someone say it was necessary to retard the ignition?

4: when hot the motor may rev up like crazy 7000rpm with no throttle, but I can fine no air leak. Will double check as there MUST be an air leak!!! Or maybe I am just way too lean?

Hi Frank, had similar problem few weeks ago. Engine was pressure tested before top end reassembly and no leaks were detected. After starting it idled ok, but after first twist of throttle started to make loud rattling noise from the right side of engine cases and idle went to 3-4 k rpm. After removing the ignition oil seal looked ok, I put the new one in and all problems were gone. I still don't know what happened to it and how such a loud noise was produced due to a faulty oil seal. So maye you should double check them.

 

[adas]

Congratulations! Hope you get the small leftover tweeks
sorted out soon. I guess the Polini head hits the piston?

Aloha, The head has .57mm clearance (and is Malossi). The knock is quite bad. I will lift the needle all the way up and see if it improves....no improvement in the knock. So back to check for air leaks.

Frank

 

[Mr.Aerox]

you are way too lean, try also a bigger pilot jet

 

[StepVino]

Aloha, The head has .57mm clearance (and is Malossi). The knock is quite bad. I will lift the needle all the way up and see if it improves....no improvement in the knock. So back to check for air leaks.

Frank

Hi frank, given the subject changed to 'knocking', I just realized
my question could be misinterpreted. I was asking in general if the
reason you used the Malossi head was that the Polini head interfered
with the piston.

 

[adas]

Hi frank, given the subject changed to 'knocking', I just realized
my question could be misinterpreted. I was asking in general if the
reason you used the Malossi head was that the Polini head interfered
with the piston.

Aloha, I guess I jumped all over the place in this thread, so let me clear it up. Not Polini head, Metrakit PS2 cylinder and cylinder head. Yes the Metrakit head comes 2mm into the cylinder and will touch the piston, so I used my Malossi head which was just the right height to give me the squish I wanted. Also the dome of the head is the same as the Metrakit head... ie same piston shape.
I think there must be an air leak as I went too rich (lumpy running at acceleration and the knock got a bit less.

Frank