Mod Ideas and seeking advice if good or not

[Street Ryderz]

These cylinders are soft aluminum with a thin flash of chrome for the iron rings to run on. If we bore the aluminum, we have to provide a hard surface for the rings to run on. Briggs and Stratton made aluminum cylinders for years, but chromed the piston to run in the bore and used special rings and aluminum to stand the wear. So for these engines we would have to re-plate with chrome or nickle/silicon or press in an iron sleeve for the rings to run on because we would have bored through the thin chrome plating.

I also have Yamaha Blasters which have iron sleeved cylinders. When worn out you just hone them to the next oversize and buy a larger piston. These engines don't have a selection of oversized pistons available. There are iron cylinders available from the Minarelli 50cc vertical engine that will fit, and they are available in a 46mm size as well. These could probably be bored up to 48 or 50mm. If you were to stroke the crank to 44mm you could get as much as 85cc. Not a great gain for all the work, it would probably make about the same HP but at lower RPM. That was my experience when I bored my Blaster 10mm and stroked it 3mm. Not much faster but more grunt, for a lot of work.

The stock Grubee cylinder it top center. Cast iron Minarelli is to the left, lower center is an aluminum Airsal Minarelli.

When you borred and stroked your blaster did you alter the gearing or sprocket to make use of the extra grunt? I know you really only go so fast off road but for guy's like me who want as much acceleration as possible that grunt would be very welcome when it out pulls the next guy!And I would think for you aswell if you were able to out pull or climb better than your buddys it proves some benifit!

 

[2StrokeMama]

There's gotta be something done to the gears I would assume, to hold rpms a little steadier... . I know when I install BBKs onto those Mina's, there is more torque forsure, but I always need to re-tune the cvt, especially with an expansion pipe to see any gains in top end.

 

[Steve Best]

When you borred and stroked your blaster did you alter the gearing or sprocket to make use of the extra grunt? I know you really only go so fast off road but for guy's like me who want as much acceleration as possible that grunt would be very welcome when it out pulls the next guy!And I would think for you aswell if you were able to out pull or climb better than your buddys it proves some benifit!

Howdy SR, yes I did.
My goal with the Blaster is unlimited off-road travel on the lightest (minimalist?) machine possible.
I had a 35hp 400 lbs 660 Raptor which is the acknowledged "Wheelie Master" of the ATV world.

Too heavy, too complicated, too fragile (motor and gearbox) and too expensive to repair. My son bought a Baster and I was impressed with it.
My first Blaster had a severely damaged motor. While I had it out, I discovered my spare 50hp 2003 KTM250SX motor would fit!
A few weeks work and an amazingly powerful ATV was born:

Imagine zero to 70mph as fast as you can shift the gears? Wheelies at any speed? Never lacking power even on brutal sand hillclimbs?
Well, all was not perfect. The close ratio gearbox meant I had to chose whether I wanted top speed or rock-climbing capability.
The liquid cooling was more complication than I wanted.
I wanted air-cooled, simple and widely spaced gears. And I didn't need 50 HP! There is such a thing as too much!
My son and I had built several Blasters, including a 32 HP Blaster with a DT200 top end.

We also built air cooled Blasters that exceeded the power of the DT200, but tended to be high rpm, lacking low rpm torque.
My goal was a torquey low rpm trail machine with about 35 HP. It would also require a lot of ground clearance.
The tall tires make for a tall effective gear ratio, but it also had to be able to crawl over obstacles, churn thru mud, and haul broken quads home.

Displacement seemed like the answer. I bought a Vito's Big Bore kit and a 3mm stroker crank for the Blaster.
One of my abiding principles is to try mods one at a time to see what works and what doesn't. So while the BBK and the stroker crank were installed at the same time, no porting or other mods were done. The result was about 25hp (butt dyno measurement!) due to the displacement and superior porting of the Vito's cylinder.

It is a minimalist machine, not a rocket like the KTM powered Blaster but a wonderful trail machine.
With only 2.5-3psi in the tires it will glide over mud and snow. The big tires do up the gear ratio and make 6th gear a cruise gear.
Top speed is about 60mph due to the soft tires. They soak up a lot of HP and make high speeds squirrelly.
(These are not the big diameter tires. Check out the last picture)

My son's stock displacement but "souped up" Blaster will out accelerate and out top speed me.
No worries, that is not what I wanted. You are right, it has the grunt to pull and climb with ease and low rpm.

Recently I swapped the head for one of my own design:

The Vito's head on the lower right was swapped for the torroidal chambered head on the upper left (stock Blaster head lower left).
The result was more torque, more RPM. Power estimate is up from about 25 HP to approx 27 HP.
To get the right squish, I used an aluminum foil, paper, aluminum foil gasket cut out of foil pie plates.
Working great!
So that is the story on the bored and stroked Blaster, and may explain why I am so slow on the Minarelli project.
That and and a lot more going on...

 

[Steve Best]

Very familiar with the minarellis I suppose the aluminum jugs are for cooling?
PS- Do you put those Mina's on your bicycle!? lol that'd be crazy, if possible.
-But to use those cylinders is very clever. Have you tried with the horizontal? Probably doesn't work, who knows tho... I never tried.

The aluminum Airsal jug is a power upgrade and it is known for better cooling.
Aluminum heads are know for allowing higher compression ratios due to better heat conductivity.
When detonation occurs, it causes a rapidly increasing temperature spike.
Aluminum heads respond well to the temp differential, cast iron does not.
Aluminum cylinders have a similar effect.

I am familiar with the horizontal Minarelli.
It has a larger cylinder bolt circle and uses a case inducted (mounted) reed. The reed has a different bolt pattern too.
It is an improvement on the vertical Minarelli, but will not fit on our Chinese bike engines without huge work.
Our 66cc bike engines are about 1.5-2.5 HP at 7000rpm stock with about 4hp readily possible at about 9000rpm.
The 50cc cast iron Minarelli starts at about 4-6HP piped at 9000rpm, the big bore maybe one HP more.
The Airsal is reportedly about 6-8HP if you include some sort of tuned pipe.
There is an even more powerful Airsal reputedly able to give 12hp but at a dangerous 13,000rpm.

Here is the hybrid cast iron Minarelli/Grubee engine:

Note that the exhaust exits from the center of the cylinder. This is a problem with mounting in most bikes.

You will notice it requires a case adaptor/spacer:

 

[2StrokeMama]

(Those ATVs look mighty fun), But Thank you for that share on the mina hybrid...You might of unleashed something here.... I never bothered to even try to see how the Mina's would fit, but yes with some careful fabbing anything can be done if your heart desires!! I totally like these setups, as Mina's are my thing I would need to look into my stock cylinders tho , as they don't have the "inducted" Reed cage, rather it sits above the crankcase , then intake , then carb , air box.
- and PS. Let me just get something straight, the airsal kit... it's aluminum aswell and I know that I've had aluminum jugs for the Mina's... so the ones on our bikes, are a SOFT - ER aluminum? This must have something with the fact that there aren't really shrouds/covers to keep on our bikes, so the softer aluminum keeps it cool?

 

[2StrokeMama]

How do the jugs heat hold up with the Mina hybrid? Do you have a temp gauge to give numbers? Did you fab something on the flywheel to direct the "air-cooling"?

 

[Steve Best]

(Those ATVs look mighty fun), But Thank you for that share on the mina hybrid...You might of unleashed something here.... I never bothered to even try to see how the Mina's would fit, but yes with some careful fabbing anything can be done if your heart desires!! I totally like these setups, as Mina's are my thing I would need to look into my stock cylinders tho , as they don't have the "inducted" Reed cage, rather it sits above the crankcase , then intake , then carb , air box.
- and PS. Let me just get something straight, the airsal kit... it's aluminum aswell and I know that I've had aluminum jugs for the Mina's... so the ones on our bikes, are a SOFT - ER aluminum? This must have something with the fact that there aren't really shrouds/covers to keep on our bikes, so the softer aluminum keeps it cool?

I have not had the hybrid mounted into a bicycle or running yet. Too busy with work, winter, Blasters and SAR.
Your horizontal Minarelli does have case mounted reed induction ("case induction").

The older vertical motor has it on the cylinder ("cylinder induction").

Notice the difference? The cylinder inducted case has an intake port on the cylinder. Case inducted does not.

The Airsal is aluminum but uses very hard nickle-silicon plating to provide a wear surface for the rings, like most modern MX engines.
Much tougher than the chrome Chinese cylinders, it can be damaged, but rarely wears out.

I do use a TTO temp guage on some aircooled engines. I haven't used it on the Grubee engine yet. It uses a thermocouple under the sparkplug.

I have had great luck buying from scootertuning.ca and scoot-tuning.com in Canada. Strongly recommend them.

 

[2StrokeMama]

Yup, that's what I was Implying the difference that it sits on the crankcase, therefor not on the jug lol sorry I'm not down on exact exact terms...but I think that's what you meant by HUGE fab work,I don't think I'd bother with all that...there goes that idea. But still... the verticals, ... scooter-tuning are my go to guys, I am always awaiting orders from them it's hard to not buy stuff from them when they are in Canada and they have great prices.
Now the question, how well The vertical jug would perform on this setup.
TTOs are the way too go just annoying how you can't swap the battery.

 

[Street Ryderz]

Howdy SR, yes I did.
My goal with the Blaster is unlimited off-road travel on the lightest (minimalist?) machine possible.
I had a 35hp 400 lbs 660 Raptor which is the acknowledged "Wheelie Master" of the ATV world.

Too heavy, too complicated, too fragile (motor and gearbox) and too expensive to repair. My son bought a Baster and I was impressed with it.
My first Blaster had a severely damaged motor. While I had it out, I discovered my spare 50hp 2003 KTM250SX motor would fit!
A few weeks work and an amazingly powerful ATV was born:

Imagine zero to 70mph as fast as you can shift the gears? Wheelies at any speed? Never lacking power even on brutal sand hillclimbs?
Well, all was not perfect. The close ratio gearbox meant I had to chose whether I wanted top speed or rock-climbing capability.
The liquid cooling was more complication than I wanted.
I wanted air-cooled, simple and widely spaced gears. And I didn't need 50 HP! There is such a thing as too much!
My son and I had built several Blasters, including a 32 HP Blaster with a DT200 top end.

We also built air cooled Blasters that exceeded the power of the DT200, but tended to be high rpm, lacking low rpm torque.
My goal was a torquey low rpm trail machine with about 35 HP. It would also require a lot of ground clearance.
The tall tires make for a tall effective gear ratio, but it also had to be able to crawl over obstacles, churn thru mud, and haul broken quads home.

Displacement seemed like the answer. I bought a Vito's Big Bore kit and a 3mm stroker crank for the Blaster.
One of my abiding principles is to try mods one at a time to see what works and what doesn't. So while the BBK and the stroker crank were installed at the same time, no porting or other mods were done. The result was about 25hp (butt dyno measurement!) due to the displacement and superior porting of the Vito's cylinder.

It is a minimalist machine, not a rocket like the KTM powered Blaster but a wonderful trail machine.
With only 2.5-3psi in the tires it will glide over mud and snow. The big tires do up the gear ratio and make 6th gear a cruise gear.
Top speed is about 60mph due to the soft tires. They soak up a lot of HP and make high speeds squirrelly.
(These are not the big diameter tires. Check out the last picture)

My son's stock displacement but "souped up" Blaster will out accelerate and out top speed me.
No worries, that is not what I wanted. You are right, it has the grunt to pull and climb with ease and low rpm.

Recently I swapped the head for one of my own design:

The Vito's head on the lower right was swapped for the torroidal chambered head on the upper left (stock Blaster head lower left).
The result was more torque, more RPM. Power estimate is up from about 25 HP to approx 27 HP.
To get the right squish, I used an aluminum foil, paper, aluminum foil gasket cut out of foil pie plates.
Working great!
So that is the story on the bored and stroked Blaster, and may explain why I am so slow on the Minarelli project.
That and and a lot more going on...

Yeah I thought as much as that sounds like a blast!light and nimble for trails and off road and that grunt would make me smile all day in tight confines when you cant go all out anyway but can walk all over bigger machines with their riders strugling!Your KTM engined one I see guys here at the track with those all modded with skinneys up front and a slick out back and they go like stink! But thats a game I just cant play anymore those guys spend 10's of thousands on their set ups and it just never ends lmfao!These kits for our bikes let me try stuff out cheaply and If I mess up oh well it cost me like 40 bucks to see if it worked or not and I get some entertainment trying in out!I am still trying to find a couple of the 17mm crank case halfs for my hybrid build I decided to go with the Stage 6 street kit it specs basicly the same as the MXS one but the secondary intake area isnt as large so I hope the area in the case where you ramped the adaptor plate can be opened with out exposing the bolt for the case halfs.I see yours is getting done looks good!The other big crank will be paired with one of the sleeved jugs that are out now but trying to get real info on them is not easy the price is not bad to me when compared to replating I could almost get two!

 

[Steve Best]

Actually I was out for a few hours on the Blaster with my son this afternoon.
The big bore Blaster is still not fast enough to beat my son's Banshee (he has 2 Blasters and 2 Banshees) for power, but I can still get ahead of him in the woods. I built mine narrow and tall and soft and I ride it like a bike. We ride like wild animals, but he excels at the jumps and wheelies. Maybe he just LETS me get ahead in the woods?

I've been to the drag track and seen the big engined quads. Drag racing is a money race anyway. My KTM Blaster is a woods runner still. I don't think I have $2000 invested in it but can easily blast past Banshees and 450 race machines. Built, not bought. The engine is actually stock. It was the most powerful 250 KTM ever made. I have a 300 cylinder for it but no sense to change it on dirt. Enough is enough.

The 3rd transfer port case area can be opened up without hitting the bolt. Do the math and figure the area. You can also drill or (grind) flatten the cylinder ring. The 50cc has lots of room, the bigger bore not so much. I'm kinda excited to try the Grubee/Minarelli hybrid, but have been so busy to see it finished.