Gently stroking the Parmakit

[Deleted]

Greetings lads! I trust all is well?

I'm state side working on a project and I'd like someone to check my math, so to speak.

The idea is to build a bit of a small frame tourer and to that end a direct reed Parmakit has been sourced coupled with a Mazzy full circle, long stroke crank.

With the head packed out 3mm the transfers are a reasonable (to me any way) 125ish degrees, and the exhaust is a solid 190 degrees (fairly rev-y me thinks). My thought to keep it torquey was to let it fart out an SIP road exhaust. Does this seem reasonable? I can't help but second guess my self.


Photos and gear ratio to follow.

Thank you.

Big shout out to Sugarlump!

[Juan]

I'd say the chances are that the SIP Road would strangle it. A Franz will work well on those timings with a broad spread of power but obviously it's around 3 times the price of the SIP pipe.

[eean]

I agree with Juan, Franz is very good, mine is ported to 189/90 and rides very well with a 28mm carb on an m1 copy kit, you can ride it nice n easy or thrash the nuts off it when you fancy it ;-)

[Deleted]

Thank you very much for your insight gentlemen. I'm going to act as if the SIP exhaust will help to keep the beast's thirst under control.

Otherwise, as promised, my other question regards the compatibility of the above set up with my overall gear ratio. I'm building this engine with a 27/68 combination giving 2.52. I'm looking forward to this brute screaming up inclines, 2 up and fully loaded. Again, I don't know how realistic that is but I expect gobs more torque over stock and it's only just slightly taller than the 2.54 it came with. So I think it seems like a pretty reasonable assumption.

If I may, by way of comparison, what set ups are people running successfully in combination with which gear ratios?

Once again, thank you.

[Juan]

Final ratio should be fine but are you shortening 4th? Not sure I'd trust SIP to supply the correct tree if going for the DRT Runner given all the trouble folks were having with those last year.

I went the other way shortening the ratio with a Polini 2.61 and a DRT short 4th but that's with a Franz, standard stroke crank and tuned Parma rotary running through a 26 VHST with powerjet. Goes plenty well enough.

[Deleted]

Thank you for yr insight Juan. The x-mass tree is as Piaggio intended. The primary is a DRT 27 straight tooth with a 68 tooth basket. The basket came with a 29 tooth primary so I can mess about a little bit if need be.

Uh, OT, can any one tell me how to post photos using Tapatalk?

[Juan]

Okay but I'd still fit a short 4th cog. Is yours the earlier or later box? You can get this for the later box, unsure if you have an earlier one. Could be worth your while going to DRT directly.