Stroker Questions

Ok I get you now about the farce head. Do you think it robs power instead of taking it then? Like should I go back to a stock shaved head?

I did start reading the MacDizzy 1989 Blaster rebuild. Already learned quite a lot.
 
na I dont think it will rob power compared to a stock head, it should perform must better than a stock head. it still has a hemispherical combustion dome and a nice flat squish band. so it is still doing the job, I just feel it would be better if it didnt have those swirls, but its probably a very minor thing we talking about here, I wouldlnt worry, if i had it, id use it!
 
I put the spacer plate back in with gaskets on both sides. It lost power. It wasn't running good before without the spacer neither but it defiantly didn't run as good or start as easy as before. Might have nothing to do with it though I dont think this carb was jetted for this engine. Still trying to learn the story behind this guys build. I going to start another thread on the jetting for this engine.
 
Ok so I measured the jug from bottom sleeve to the top gasket flange on both the original (thought may have been shaved for McDizzy theory) and a known stock jug. They were both the same. This just confuses me. Why would someone ever add a spacer at the base for no reason???
 
well then to confirm this you should in theory have low compression, as well as a very big squish band.

What is your comp? can you measure the height below the barrel deck the piston sits at TDC. use a feeler gauge to get this and be very careful to get it at TDC
 
Ok, well here is what to look for:

your stock deck height with a standard 0.5mm oem gasket under the barrel is -0.63mm (meaning 0.63mm below top of cylinder)

by adding a 0.9mm spacer it then becomes: -1.53mm (this is without another base gasket as your setup was)

by correctly adding another gasket, this is pushed to: -2.03mm

if you find this measurement with 2xgaskets and the spacer, it means the chop who did it didnt have a clue what he was doing. he effectively improved the port timing but then severly lowered the compression so much that it was pointless.

your ideal squish between piston edge and head edge at TDC on a 200cc is around 1.1mm. you can see that already without including the head gasket thickness, yours may be 2.03mm more than double what it should be.

add the 0.8mm thick head gasket ans that turns to 2.83mm squish. this is useless. luckilt the head has been done or else the stock head would retard this even further and it probably wont even run.

To fix this, either simply remove the spacer since your barrel is stock and run it with the head. But if you want to pursue the Mcdizzy route as I did, you will need to habe the top of the barrel machined and according to my sums, 1.75mm needs to be removed from the top. this will then correct the squish to optimum and the compression while maintaining the best port timing you can get.
 
forgot to mention then that as your target squish is 1.1mm and your head gasket is 0.8mm and you have no step or recess on that head, it stands to reason that your required deck height is -0.3mm

to get this when your current deck height with 2x base gaskets and a spacer is 2.03mm we then subtract the required deck height of 0.3mm to give us the amount required to be cut off the top of the barrel thus

2.03mm-0.3mm=1.73mm

tadah!
 
Thanks Blaner! I removed the spacer and installed a new base gasket. Im getting 116 PSI now. Also the weak power problem turned out to be that that 33mm PWK was too big for this set up. Went to a 28mm PE and runs much better.