Midrace - Racing Setup (Beta Ark LC)

You can also go with lower weight rollers. However, when you choose too light rollers, the engine over revs and you won't have any power at all. That's why it's better to start with heavy rollers, as it ensures, that you get into the right power band for your cylinder/exhaust combo.

Here's a video with pictures of a flowed Minarelli Engine. If you can show this to your mechanic he should be able to ensure a proper gas flow and you'll get some free hp and increased torque! (Turn off the speakers to avoid horrible music :)

http://www.myvideo.de/watch/6585057...uer_Hebo_Revolution_Patanegra_High_End_Tuning
 
Seems ok. It ran a bit hot on the exhaust bridge (in between the T). Malossi recommends to grind down the bridge slightly. I guess this wasn't done, but it should be fine now. Do you ahve a new piston/piston ring?

Cheers,
D
 
I'll buy a new one. I just have to figure out which piston it is because i'm going to use it with a 10mm crank, so i have to know the dimensions. Any tips on this one?
 
Unfortunately i already have a Malossi RHQ 10mm, so buying abother 12mm would be just a waste of money. The problem is that Malossi does not produce 10mm single ring 47.6 pistons. I think so.
 
I guess you're right... You can go with the Stage6 or Athena pistons... They are all 47,6mm and as far as I know the Minarelli MHR doesn't have inlet holes in the piston, right?
 
I dont think so, it's a regular 47,6 one. The problem is which from stage6? AA BB OR CC. That has to do with the cylinder size itself. I believe it is an AA, but you never know.
 
Apparently the size C works well. However, the AA BB CC sizes are usually used for replacement pistons after the cylinder itself was overhauled (new coating, etc). Size C means they are slightly bigger to overcome the loss of material (due to honing and coating). Thus the C size piston would be the biggest... TBH I'd go with the size A to be safe. It will work, no doubt...
Have you checked your cylinder? It should also have some indicator which Malossi piston size was used...
 
Strangely i checked and the piston and it's Malossi branded. I measured the gudgeon pin with a ruler and it's not 1.2cm, so i assume it's a 10mm.
 
Try a caliper, the ruler method is really bad. You can get these digital calipers for less than $10 on ebay and they are good enough for casual use! This way you can then also measure the cylinder diameter and choose the right piston.
 
I used a polini evo piston, in my old Firefox. I Also had 10mm.
Big difference between malossi and polini pistons is that the evo piston spring is harder than a mhr spring.
Example.

In my Firefox with original evo cilinder & piston. I drove 7000km with good compression.
With the mhr piston in the evo cilinder I lost compression after 2000km.
After a while I changed the cilinder 2 a normal mhr cilinder..
Compression was lost after 1500km.
After changing the pistonrings 2 a polini evo pistonring, I drove more than 3000 km with them..

Firefox setup was.

Polini evo 1 lc cilinder, later mhr lc cilinder
Mhr exhaust.
21mm dellorto
Malossi overrange kit.
Malossi mhr deltaclutch.
Mhr multivar.

I used the scooter as a daily driver..
 
So you recommend buying a Polini piston for my mhr cylinder ? By the way as a daily driver how was the MHR with thr MHR Exhaust? What about performance?
 
You wil have 2 compare them. I dont know if there have been changes in the pistons with exhaust port or something like that.
I had original ignition, with a malossi cdi.

Performance was great. I never got caught
 
Did you have to get the revs up a lot? I mean was it a peaky setup for the street or was it bearable? What do you think about the C16 on the MHR Cylinder?
 
Did you have to get the revs up a lot? I mean was it a peaky setup for the street or was it bearable? What do you think about the C16 on the MHR Cylinder?


12.500/13.500 rpm
I also had a c16 under my f15 went great.
The scooter used up a lot of tires, weights, belts, brake pads and fuel... Especially the last thing...
Tja 21mm...
 
Hey, so my scooter is currently at the mechanic as the reed petals have broken , thus too much gas is going into the engine causing it to bog and kill when it revs. Anyone, i was thinking it's a good chance to change to the MHR cylinder now. I just haven't decided about the exhaust. Could you help me a bit more? What will be the differences in driving style? Also should i change rollers and belt? I have only drove 1000 km with the current ones.
 
interesting, i'll wait & see what happens. good luck with whatever choice you make, it doesn't matter what parts you got, it all boils down to the person doing the tuning.
 
Hey, so my scooter is currently at the mechanic as the reed petals have broken , thus too much gas is going into the engine causing it to bog and kill when it revs. Anyone, i was thinking it's a good chance to change to the MHR cylinder now. I just haven't decided about the exhaust. Could you help me a bit more? What will be the differences in driving style? Also should i change rollers and belt? I have only drove 1000 km with the current ones.

There is a good chance that you need different rollers, changing the belt isn't needed. Also you might need to change the compression spring. But thats all guessing, you have to fit the parts and see how your scooter reacts and adjust accordingly.
 
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