beebone

Anyone tried to put a 9 ports sleeve into the engine case which is for 7 ports?
I have a Flash 21, the crackcase going bad, want to put the P/S into Kangaroo engine case.

DJ_Shakespear

If it was me, I would (try to) put it in and then see if everything lines up correctly.
But you have to consider:
Is the stroke the same between the Flash and Kangaroo?
Which crank are you going to use - are they interchangeable? Are the crank pins the same size as each other?

Im just asking these in my POV, and because I dont own either of the 2 engines

Roelof

It will fit, the only thing you have to check if the piston is at BDC the top of the piston does align with the under edge of the ports. Use the button head of the 9-port sleeve and always cheack the real head clearance with a piece of solder.

beebone

Yes, those are same stroke, both using R7 conrod.
For sure I will use Kangaroo crank (14mm) because the conrod pin on crank worn out, so the glow plug on F 21 burnt always. So give it a try to move the 9 ports P/S to Kangaroo.

beebone

Yes, thank you. Will see how it goes.

DJ_Shakespear

Roelof, i hope this doesnt turn out weird or sound strange, but every time you mention putting solder in to check the head clearance, for some reason I have a giggle about it! Not in the way that I think it's silly or a dumb idea, but just a funny feeling - I don't know, just thought I'd let you know

It doesn't matter what length the rod is, the stroke won't change. If the crank has a larger rotation path, then the stroke will change (not sure if that makes sense) What Im trying to say is if the distance from the crank pin to the center of the crank (on the Flash) is further than what it is on the Kangaroo, the stroke will change, and with that it will perform differently. I dont think this will happen, as according to the Novarossi site (comparing the Flash 21 Special, and the Syd Kangaroo) they have the same stroke.
Just like Roelof said, see if the piston sits (at its lowest point) right on the bottom of the exhaust port. If it doesnt sit exactly flush, it's not a real problem, but it will perform differently (could be better than stock) and you should check the head clearance as well.

Roelof

All current Nova's are using the R7 rod so no need to be scared, also all .21 racing engines are useng the 16.2x16.8 bore/stroke and all .21 engines are using a 19.5mm sleeve

Grinder

iTrader: (2)

It works. I have tried it. You have to use the 9 port button with approximately .4mm of shims to get the correct head clearance. The wristpin on the 9 port pistons is higher than kangaroo piston. I found the best performance was using a kangaroo piston, with the 9 port liner. This is what Maxpower engines used on the TQ9. Although both setups ran well.

beebone

Woo will try tmrw, thx!

beebone

Tried this afternoon, basically the piston can pass the exhaust port completely, the con rod rotation no problem. The only thing have to fine tune is the compression ratio.

The sleeve of F.21 PT, the crown of the sleeve is 0.5mm thicker than Kangaroo sleeve, when the sleeve complete insert to the engine case, there is no flush surface. It means the combustion chamber increase in 0.5mm, no need to add 0.4mm shim, in fact, i have to maintain or using less head shim to offset the increased volume.

Grinder

iTrader: (2)

Yes. You have to remove shims. Instead of using .70mm, we used .40mm of shims as stated above. Not adding an additional .4mm. Actually removing .30mm, and that was to make a high head clearance. If I remember correctly that made the actual clearance around .55mm when checked with solder.

beebone

Thx! The engine sound become healthy now