keuk

Dammit ! The answer is in front of me, I have machined the primary for the DRT repair kit, so the housing in the primary is bigger than is the Hartz plate and bell... so it is a pain in the ass to mount it, I'll try to find another primary gear to check.

Hello, I need to mount the primary and the repair kit alone in the engine casing ( the bell doesn't pass), but it's very touchy to make the springs fit, so I can't imagine in the casing. It's very hard to keep the spring in place when I remove the two screws. Do you have a trick ? I use DRT spings.

Wow ! Geil! Any pictures of the exhaust ?

Well...nice job ! The transfert in the casings are not even matched with the cylinder ? And you kept the flange inside the transfert ports ?

Then WOOAWWW Great !!

51 stroke ! ?

What does that mean ?

Hello, for a race use, I would like to use a longer 1st and 2nd, is it smart or not to combine it with a DRT runner christmas three with its shorter 3th and 4th ? I'm afraid that the gap between 2 and 3 would be too short ?

I'm going to add a piece to block the rotation like on the following picture, right now it's just fixed with the upper bolt of the U clamp.

Problem solved temporarily

Original VS SIP... WTF ???!! Not really P'N'Play

Allright but do you guys change because of the carburetor size limitation of the Polini or also because of the position of the carburetor ? I mean, does the carburetor fit correctly in the frame with the Polini ?

Hello, is it obligatory to use the falc intake to mount le carburetor correctly in a PV frame ? Are there pictures of the assembly ? Thanx !

Still on development , all the advises are of course welcome, right now it's just an original casing whith the standard thickness, crankshaft room, bearing. The transferts are bigger, and of course, as you can see there is an access to the gearbox.

What kind of braking fluid can I use with the Stage6 4 piston caliper ? Dot 4 or 5.1 ?

Is anyone using a steering damper on his racer ? Do you have advices, pictures of your assembly ? Thank you.

I realize that I had the same question about the compression ratio found on the SCK blog. I did the test on a 3D model considering a squich of 1,2 and the bump of the piston head and the exact geometry of the cylinder head, and i'm more close from the polini data sheet. I found 13,4:1 for my 53 and 13,0:1 if I change for a 51.

That's interesting ! One question, on the blog link, for the volume found on the new and the old polini cylinder head, on the old model there is a gap after the squich band on the new model there is no gap, is it really comparable ? Shouln't we use the squich value for the volume of the head to make the ratio? Sorry i'm novice for with this compression rates.

I see that you are talking about the compression ratio, Is it important to change it if I use a 53 stroke instead of the 51? I didin't modify the geometry of my cylinder head on my evo.

I have a theory... I have compared the sprinter and a standard mazzu on illustrator.. The moment where the path for the gas mixture is fully open is very late on the Sprinter, the piston is near the TDC, and his linear speed is very low, so the volume of gas mixture that is sucked at this moment is reduce. Ok the mixture can enter before but not with a good flow. On the mazzu, when the path is fully open, the piston still have a good linear speed, and the volume that is displaced is bigger. Ok there is nothing really new, but I should maybe look on this side, adding a big chamfer on the DRT or using a mazzu, no ?

Yes it should be interesting to make this new tests, I keep that in mind for the next time, I should proceed more methodically, last time I had access to a long period to the dyno, I only focused on the main jet to gain few hp from 18,.. to 21. It's a bit frustrating to realize that I had the same power with an iron polini, a bent standard 51 mazzu, a throttled exhaust port, a small koso 28 with mini tassi and a longer transmission ... Dammed

I'll try a 35 and a new exhaust. I'll also reduce a little bit the squich, I have 1,2mm right now. Here is the curve of this week end.

Thank you for the reply, I'm tempted to try a bigger carb and another exhaust but what about the crankshaft ?, isn't the DRT sprinter too restrictive for the mixture ? Is there a better solution available on the market ?

On my racer's evo with 127/192, DRT sprinter 53/105, Keihin 33, 70%, franz, vespatronic, I have 21HP at 8800 and the engine doesnt' go further than 10200, that's quite good for racing but I would like to understand how some of you can achieve a way more hp than that, I think I saw a 30hp on this thread. To go further, is it necessary to modify the portmap of the cylinder, and to increase the height of the intake transfert in the barrel to increase the volume of gaz that can enter in the barrel ? What could be the most efficient point to work on, the crankshaft ? Remove the quicksteel in the casings transferts to increase the volume ? increase the diagrams ? Try another exhaust ? work on the compression rate? Here are my last year curves, I made a dyno test this week end without improvement, I had optimized the exhaust port and the intake. (I will upload the new curve later). The dyno is a softengine, it's a bit more severe than the P4, apparently 1for10hp.

I have added a RS24 on the googledoc link.