GPR Camp: Replica Racers

It’s coming along nicely. Awesome project!

Uh yeaaah, about that... i had to pull apart the engine

kaldis12 wrote: ↑

Tue Nov 26, 2019 5:26 am

Uh yeaaah, about that... i had to pull apart the engine

The dangers of flying close to the Sun.

Just a little quick update.
Im done with the designing. The new crankshaft and clutch(the straight teethed one) is on its way, as promised about a year ago.

Are you actually going to be making these yourself?

The crankshaft will be made by Team35 who is known for their high quality stuff. They make even cylinders for derbi and am6. Probably they produce the best cylinders.

As for the clutch, I have no idea right now. Propably by my friend. We will make a few ones maybe.

That's cool, I have a Team 35 crank I got I guess 5 years ago along with a cylinder that was matched for the new stroke.

I would make it myself but nowadays I dont really have access to these kind of tools.

I will go with a 47mm stroke with 94mm conrod.
Changing from 44mm stroke and 85mm conrod.

I've found stress above the exhaust port that indicates that the conrod is too short. Also I need to lower the transfer durations as now Its like 135 degrees. Which is a lot. Going for 129 degree transfers and 198 exhaust. Better low end and slightly stretched power range.

kaldis12 wrote: ↑

Wed Jan 01, 2020 11:49 am

Also I need to lower the transfer durations as now Its like 135 degrees. Which is a lot. Going for 129 degree transfers and 198 exhaust. Better low end and slightly stretched power range.

Aren't those timings a bit mismatched, ie transfer timing much lower than exhaust? I only say based on recommendations for my NSR from an experienced tuner. So I ported mine to 190/130 and was suggested max of 195/133 which this guy has on his 48mm x 44mm setup which does 98mph at moment, he's aiming for 100mph.

That said I have a cyl ported by Team 35 which is 198/135 which he felt was too high.

The stock timings are really off the road.

Mines are the best for my purpose. The aim would be 130/200 degree. Thats kinda a golden road for both wide powerband and power. But I want a bit lower rpms, so I go with a slightly lower exhaust duration.
With lower transfer duration my overrevving will be a bit more though, so it will kinda balance it out for my purpose.

135 degree is way to high for transfers IMO. I like the lower 128-130 degree range way better for 198-200 degree exhaust

My aim is 100mph(160kmh) too. With the old timings I was able to achieve 90-93mph. Revved about 14000rpm.
Expecting to better though.