mhr rep *Tuning*

[muhuha]

Im after even more power with my mhr rep cylinder, im running a crappy derestricted standard pipe which isnt fast atall but will be getting a mhr team2 on the cheap pretty soon, for it to work i beleive i have to tune my cylinder for a higher rpm? and my aim is to get 15bhp+ . Could sum1 tell me how i can tune the cylinder to get this power.

:winner:

 

[hac]

on MHR replica timing is to low,somting like 113°/173°,i use plate under the cyl to rise tranfers/exaust timings and riseing and widening exaust port on 128°/198°........this timings is for peuget MHR replica ......look at my project page http://forum.scooterforum.net/forum/f88/trekker-lc-142798/

 

[muhuha]

How do you measure timings? Cant i just go on widths and heights? Either way i have to make them higher and wider, could you tell me how much and can i obtain and power from the transfers or other ports? I dont fancy matching the transfers because id have to dis-assembles my whole engine which i am not doing. Any other tips and tricks i could do?

 

[hac]

yuo must measure your timings,simple because i have MHR replica for peugeot and timings on mina and peugeot MHR replica cyl ......i think it's not same

 

[Big B NRG]

If you don't know how to measure your timings, I don't think you should try to tune your cylinder. If you going to do this yourself, you won't reach 15 bhp.

Mina MHR-R is quite fast stock. With some setting up + good parts matching, you should could reach 15 bhp.

 

[muhuha]

Well ive got all the basic mods on there at the moment-17.5mm carb, reed valve, crank, all transmisson mods. How are timing measured then? Seeing as you measuring in degree's you measuring angles then? I just want the cylinder to work on a malossi team2 pipe, and all i know is that i have to raise it for higher rpm's.

 

[Big B NRG]

Well ive got all the basic mods on there at the moment-17.5mm carb, reed valve, crank, all transmisson mods. How are timing measured then? Seeing as you measuring in degree's you measuring angles then? I just want the cylinder to work on a malossi team2 pipe, and all i know is that i have to raise it for higher rpm's.

You can either measure timings with a degreewheel or a caliper.
With a caliper you measure the distance between top cylinder port - cylinder deck.

That value you get you enter in a formula (search the web or see Bell's tuning book) and you get a timing in degree.

It's not just raising the timing on your cylinder. Going higher in timing, requires higher transfers, different angles etc. Also you would need a new carb, since your 17,5mm carb is way to small, for the RPM's your scoot will be doing after tuning (to match the exhaust). Tuning 2-stroke cylinders listens kinda carefull. It's not 3 mm here, different angle there, some wider here.

Best is to get a different cylinder + setup if you wanna use the Malossi exhaust, get a different exhaust to match your current setup or get your cylinder tuned by someone who know's he gets result from tuning.

Read the books and the web, plenty to find about tuning your 2stroke engine. We cannot give you a custom made, tailer fit answer for your question.

 

[muhuha]

Rite, well im trying to understand this as a example if from top of port to cylinder deck was 22mm and that =136degrees, and then to get 186degrees i has to type in 19mm into the equation i have to raise the port 3mm correct? Do i raise the transfers the same 3mm and how do i tell what angles they are to be put at?

As for a carb i have a 21mm lined up.

 

[hac]

men,this forum is full of information,try same reading and you find all you need

 

[muhuha]

im looking im looking!!! theres nothing on liquid cooled mhr rep porting, cant find the standard minarelli stroke, port timing isn't easily explained, but ive got a online calculator. Transfer ports i havn't yet looked.

ALTHOUGH i have looked and i can just port the exhaust port by itself apparently which is what i wanted to do.

 

[hac]

standard minarelli stroke is 39,20 mm.try searching for "porting" not MHR replica porting......theres no blueprint for porting MHR replica cyl

 

[adas]

Aloha, the MHR Rep is very good as it is. You will have to have a lot of experience to make it much better. The side boost ports can be made larger, and if you raise your timing, you will have higher RPM's but not a much better power curve. You will loose some torque on the bottom end. If you want a sprinter, then OK to modify the cylinder, but if you want a screaming stoplight street runner, leave the ports alone. Or get a Metrakit cylinder.

frank

 

[Big B NRG]

You check out this link with the download;

http://forum.scooterforum.net/forum/2518424-post47.html

Should get you started on timings.

 

[muhuha]

Im not going to modify loads and loads lke 14-15K rpm more like 12-3K rpm, So going on what everyone has said i can now work out timing!!!! Could you give a timing that will work well with the team2 pipe if anyone knows?

I intend in raising the transfers to 31mm deck clearance and then raising the AUX EX ports to the same as the main port which i will raise to the giving timing. (22mm most probs, i will find out standard deck clearance).

More input appreciated im learning!!!

 

[silver_flame]

I think i saw on the dyno's that Team exhaust peak power & torque is around 13500-14000rpm.So my guess is if you want to tune the cylinder to the exhaust you should tune it to work fine on those revs.

 

[Big B NRG]

Im not going to modify loads and loads lke 14-15K rpm more like 12-3K rpm, So going on what everyone has said i can now work out timing!!!! Could you give a timing that will work well with the team2 pipe if anyone knows?

I intend in raising the transfers to 31mm deck clearance and then raising the AUX EX ports to the same as the main port which i will raise to the giving timing. (22mm most probs, i will find out standard deck clearance).

More input appreciated im learning!!!

Do you have the proper tools do raise transfer timing? You cannot use a dremel of any kind.

If you only raise the exhaustport your Blowdown will be to high and you will have shit driving cylinder.

If you want more power, raise the aux ex.ports to the same level as the main exhaustport. That you can do with a dremel and some patience.

Won't be perfect with the Team exhaust. But will give more power.

 

[tiba_karotsu]

i can raise the transfer ports with my dremel but it takes a lot of dexterity & technique to accomplish, i ordered an angled handpiece just to make porting the transfers a lot easier.

 

[Rage]

i can raise the transfer ports with my dremel but it takes a lot of dexterity & technique to accomplish, i ordered an angled handpiece just to make porting the transfers a lot easier.

Who makes the angled hand piece to fit a dremel? All the ones I've looked at don't fit dremel motor/shaft drive.

I had to buy motor,shaft and handpiece from the states.

 

[Browni]

Who makes the angled hand piece to fit a dremel? All the ones I've looked at don't fit dremel motor/shaft drive.

I had to buy motor,shaft and handpiece from the states.

If you already have a motor + flexible shaft, I think it wasn't' necessary to buy a new kit for a handpiece.

For example I have a simple Ferm 135W machine with it's own flexible shaft. I cut of the fix straight (plastic housing) handpiece and made an adaptor for the Foredom quick change handpieces. I made the adaptor from aluminium and I inserted two small ball bearings too, so it's industrial quality, reliable and cheap solution. I use a Proxxon pedal so the kit is complete.

 

[muhuha]

What tools besides dremel do you use, i was going to use a file set, really dont fancy a slip with a dremel, also can you give me a good exhaust port timing to work with the team2 pipe.