My mod 45cc piston

Teejay112

Well-Known Member
Messages
218
49539
On the right is my high rev modified piston
49540
As you can see the piston has been ramped and trimmed on the intake side of the skirt this has allowed me to reach 18000+ rpm I have also ported the cylinder in a totally weird way I raised the transfer port by 1cm and extended it towards the intake because there was still enough space for good compression in the cylinder as I was experimenting i also added a small boost port keep in mind the other transfer port remained untouched as I didnt know if I was destroying my engine or not 4954449545when I did this I noticed a huge increase in torque and rpms and also a different engine tone I was also able to tune the engine leaner than usual heres a look inside the cylinder like I said all I did was experiment and I got huge gains from it I decided to tear the engine down because I will be putting a new piston ring in I have also got a new pullstart coming because I want to do a neater job on the venting as bad as it looks its smoother and polished over and runs great 49541
 

Seandonato73

Well-Known Member
Messages
1,199
Shame it's an open transfer system. Looks good other wise. Idk if its from the open transfer or not. but normally when you raise the exhaust port or window the piston you gain top end and lose bottom end. Simple reason there is less time for expanding gasses to push down on the piston before they start to venture out the exhaust. Any way glad it's working good for you!
 

Teejay112

Well-Known Member
Messages
218
Shame it's an open transfer system. Looks good other wise. Idk if its from the open transfer or not. but normally when you raise the exhaust port or window the piston you gain top end and lose bottom end. Simple reason there is less time for expanding gasses to push down on the piston before they start to venture out the exhaust. Any way glad it's working good for you!
Minor loss in bottom end still tries to lift the front but q big gain in top end it screams like a smaller engine pulls away instant so was worth the work but now I'm just waiting on gaskets and a piston ring and a pullstart cant wait to get it running again
Nice 👌👌 now I really want to try ramping my piston to see if I can get higher rpms
It's worth it but I'd say it's always good to have a backup piston
 

Z.hb71

Well-Known Member
Messages
2,942
Location
Manvel, Texas
Minor loss in bottom end still tries to lift the front but q big gain in top end it screams like a smaller engine pulls away instant so was worth the work but now I'm just waiting on gaskets and a piston ring and a pullstart cant wait to get it running again

It's worth it but I'd say it's always good to have a backup piston
Yeah it's probably a good idea, sucks that it's $80 per piston
 

Seandonato73

Well-Known Member
Messages
1,199
Z don't bother. Youll be able to gear a yours up so much the lower rpm wont matter.

Teejay. Glad your getting the results your looking for! Always fun for me to see someone dive into one of these not afraid to try stuff out.
 

Z.hb71

Well-Known Member
Messages
2,942
Location
Manvel, Texas
Z don't bother. Youll be able to gear a yours up so much the lower rpm wont matter.
Ok 👍 hoping for 16500k for the final set up without porting on my engine. Don't really want to get it ported becuase when the time comes and I need to replace the cylinder, then u have to get it modified and all that.
 

Seandonato73

Well-Known Member
Messages
1,199
Yeah I don't think you'll really need porting with the power yours should turn out lol. You'll have enough problems keeping the drivetrain together lol.
 

Teejay112

Well-Known Member
Messages
218
Yeah I don't think you'll really need porting with the power yours should turn out lol. You'll have enough problems keeping the drivetrain together lol.
That's true 71cc no need for any tuning tricks just really big gears
 

Teejay112

Well-Known Member
Messages
218
Now I know the basics of porting I'm going to go a little further on the porting as the engine still has a lot of torque I've gone up 3 teeth on the pinion and down 1 on the spur not much but I have enough power to do 4wheel burnouts on dry tarmac and the car believe it or not wants to drag my arm off if I hold onto it so I will lose a bit more compression to gain more top end intentionally I'm aiming for 19000+ rpm and enough torque to still launch the car on any surface with the wheels still spinning and gear up again i do a lap around the local car park just on acellerating on a straight I get smoky smelly burning tires.

So far the rovan 45 has outlived most peoples expectations in power and reliability its had 20 litres through it now and this will be the second time I change piston rings and also bearings this time and to survive this long with my kitchen port work and worn out burrs and polishing bits that's a result even with a pipe rated upto 32cc this thing just never gives up unless it's out of fuel

One day I'll have a rcmax or alx no obr or oddifield or g4z for me or trevor Simpson I think I can f with an engine enough to either destroy it or make more power no research just trial and error .

That's alot of writing wow
Unless it's a drag racing engine which mine is not
I'm building mine to be a drag engine with good top speed and still have alot of off road power
 

Z.hb71

Well-Known Member
Messages
2,942
Location
Manvel, Texas
Now I know the basics of porting I'm going to go a little further on the porting as the engine still has a lot of torque I've gone up 3 teeth on the pinion and down 1 on the spur not much but I have enough power to do 4wheel burnouts on dry tarmac and the car believe it or not wants to drag my arm off if I hold onto it so I will lose a bit more compression to gain more top end intentionally I'm aiming for 19000+ rpm and enough torque to still launch the car on any surface with the wheels still spinning and gear up again i do a lap around the local car park just on acellerating on a straight I get smoky smelly burning tires.

So far the rovan 45 has outlived most peoples expectations in power and reliability its had 20 litres through it now and this will be the second time I change piston rings and also bearings this time and to survive this long with my kitchen port work and worn out burrs and polishing bits that's a result even with a pipe rated upto 32cc this thing just never gives up unless it's out of fuel

One day I'll have a rcmax or alx no obr or oddifield or g4z for me or trevor Simpson I think I can f with an engine enough to either destroy it or make more power no research just trial and error .

That's alot of writing wow

I'm building mine to be a drag engine with good top speed and still have alot of off road power
I think I want a rovan 45 now 😂😂😂
 

Seandonato73

Well-Known Member
Messages
1,199
Wonder if you could pit a 47 cc or 50 cc off a saw on it?? Closed transfers would benefit your porting a good bit.
I'll have to go on my lap tip when I get a bit more free time and post up a few porting links for you to review. They're for saws but same principles apply here.
 

Teejay112

Well-Known Member
Messages
218
Wonder if you could pit a 47 cc or 50 cc off a saw on it?? Closed transfers would benefit your porting a good bit.
I'll have to go on my lap tip when I get a bit more free time and post up a few porting links for you to review. They're for saws but same principles apply here.
Thanks I been looking at chainsaw Cylinders and pistons but I've had no luck
 

Seandonato73

Well-Known Member
Messages
1,199
Here are a few threads on porting. This one applies to a 46/50cc don't know if it's the new edition or not. These are modded more for torque then top end rpm but you should find them informative.
https://www.arboristsite.com/community/threads/mastermind-revisits-the-346xp.230531
You'll get sick of me posting about this guys... hes considered a genius for port mudding. Explanations of why he does things.
https://www.arboristsite.com/community/threads/wanna-talk-about-port-shapes.260764/page-2
Misc terms and what not
http://dirtrider.net/forums3/threads/cylinder-porting-basic-principles-by-eric-gorr.185105/
Zen how to guide.... for what its worth.
https://www.modelgasboats.com/magazine/tech-articles-mainmenu-608/72-engine-porting
 

Teejay112

Well-Known Member
Messages
218
Here are a few threads on porting. This one applies to a 46/50cc don't know if it's the new edition or not. These are modded more for torque then top end rpm but you should find them informative.
https://www.arboristsite.com/community/threads/mastermind-revisits-the-346xp.230531
You'll get sick of me posting about this guys... hes considered a genius for port mudding. Explanations of why he does things.
https://www.arboristsite.com/community/threads/wanna-talk-about-port-shapes.260764/page-2
Misc terms and what not
http://dirtrider.net/forums3/threads/cylinder-porting-basic-principles-by-eric-gorr.185105/
Zen how to guide.... for what its worth.
https://www.modelgasboats.com/magazine/tech-articles-mainmenu-608/72-engine-porting
Thanks the last link the zenoah one that's the one I originally saw that encouraged me to take the dremel to the cylinder
 
Top