POLINI 210 ALLOY

[Davidsquaredson]

The rally engine head doesn't have the clearance of a PX. Undoing the engine bolt and pivoting just allowed the swapping of the head.

For jetting. I've got rally200 engine, sip road 2 pipe, bgm 26/26 carb, drilled 2 holes in airfilter.

Base main jet is 118. My guess is

+8 for polini. +8 for exhaust. + 2 for filter. So I should try a 136 main jet.

Will try it out tomorrow and report back.

David

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[jonny snatchsniffer]

yes ive used one recently, i got the 58mm stroke version, i too had trouble with the squish, the lowest i could get it was 2.1mm which was without base or head gasket, 2.1mm squish would have been s**t, and the transfer timing was way to low at around 115 degrees, after an arguement with sip over whether i had the 58 or 60mm version it was determined i had the 58,
i wasnt going to get the barrel cut or skim the head so fitted a 60mm polini crank which had a little to much inlet but using that i got the squish down to 1.1mm which was my aim for this particular motor.
i raised the exhaust port to 185 and set the transfers at 128 and an inlet of 185 in total and its sweet as a nut.
T5 carb with drilled out filter and 135 main standard pilot but really need to go up 1 or 2 sizes

[eibargum]

The rally engine head doesn't have the clearance of a PX. Undoing the engine bolt and pivoting just allowed the swapping of the head.

For jetting. I've got rally200 engine, sip road 2 pipe, bgm 26/26 carb, drilled 2 holes in airfilter.

Base main jet is 118. My guess is

+8 for polini. +8 for exhaust. + 2 for filter. So I should try a 136 main jet.

Will try it out tomorrow and report back.

David

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I think 8 for the SIP might be over the top David, I went up 4 for the SIP, iam currently running a 130 main, that's the biggest main it will run cleanly with. I haven't altered the air filter though.

[Davidsquaredson]

I've got it dialed in now. My main stack is 160, be3, 135 main. My pilot is a 38-120. It is very slightly rich around 1/4 throttle so once it's broken in I'll try a different slide. But I could leave it as is. Things improved a lot with a pilot jet that had a more narrow band of effect, probably before was overlapping but my big main. I've attached the best chart I've found about pilot jets.



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[eibargum]

Mines rich at the bottom end with a stock 55/160 pilot in when using a big main, thinking of going leaner on the pilot, i could maybe then go up on the main to a 135 because I could do with more plug colour higher up, I,v noticed when looking into the carb that the main comes in as soon as the slide moves, is this normal on a Si carb.

[Davidsquaredson]

Mines rich at the bottom end with a stock 55/160 pilot in when using a big main, thinking of going leaner on the pilot, i could maybe then go up on the main to a 135 because I could do with more plug colour higher up, I,v noticed when looking into the carb that the main comes in as soon as the slide moves, is this normal on a Si carb.

If you look on a picture of where jets have an effect from 0 to full throttle, each is an overlapping oval. It's why you always start at one end with jetting. This was my problem, the big main had a long oval as did my pilot, they overlapped. Was not an issue when I had a 118 main. Narrowing the scope of my pilot did the ticket.

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[eibargum]

Most, if not all wright ups I,v read on Si carbs say the main doesn't come into play until around 1/3 throttle, but looking into the carb this is not the case, as I,v said as soon as the slide moves fuel starts to come through the main, not full bore but it does start to flow. Just a point of interest, when I imported my P200 in from Spain, it came with a 116 main & a 50/160 idle jet & to be fair it ran well, I think I,ll replace the 55/160 with the 50/160 before uping the main & see if it cleans up the bottom end. All interesting stuff.

[Davidsquaredson]

After much frigging around this is what I settled on: 132 main. 160be3. 62-160 pilot.

That’s with a new 210 ALU barrel and head. Bgm Si26 carb. Drilled air filter. Sip road 2 exhaust. Case is not matched to barrel.

And I love this kit.


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