Decided im keeping my EURO after last weekends disapointment on the RMX.
Back to the Gassers, only took me 6 months to work it out.![]()
What happened on the RMX Col?
Decided im keeping my EURO after last weekends disapointment on the RMX.
Back to the Gassers, only took me 6 months to work it out.![]()
Dont worry about the work, its more important to set it up the way you want... and maybe i was a bit pushy with my opinion before, id forgot that youre keeping the 300 cylidner as well so theres always the option of setting up the 250 as the top end screamer and setting up the 300 as the torque monster for when you feel like riding different animals. I guess what i was pushing for was setting it up as an allround bike, but maybe thats not the point here. Its not like running the 1.3mm gasket stack will be bad, its just going to be more of an MX style delivery compared to the enduro delivery of the stock EC.
Ill get back to you about the 300 specs... have to look at my notes first.
Just a point to remember comparing gasket thicknesses; They compress. So a like a 1.3 when all screwed down will lose 0.1, 0.2, so you have to measure the effect on the metal bits once you've added or removed the gasket.
It would be interesting to know what the diff in the 300 to 250 porting was. Bearing that they seem to run the same carb & pipe, riding the 250, I find it too aggressive for me, whereas the 300 is a pussycat. . .well unless you leave the throttle on too long, & then it bites.
so what are you going to end up with as a squish clearance? & what comp ratio?
The Black line is the stock engine, in this case 2.5mm squish, 11.9:1 comp, 1.3mm base gasket stack, piston level with port floors at bdc
The Red line is the cylinder dropped by 0.7mm to give a squish of 1.8mm, no further changes other than what occurs by dropping cylinder.... comp increases, exh duration drops, transfer duration drops
The Green line is the cylindner dropped by 1mm to give a squish of 1.5mm, no other changes.
The Blue line is dropping cylinder a bit but then doing some basic mods to the exhaust port to bring the top end power back... best of both worlds... better bottom without the loss on top. You can take this much further to get better top end if you want.
BLACK line is stock engine
RED line is 1.6mm squish, 13.2:1 compression, done by machining head only
cause Jakobi asked for it
GREEN line is cylinder dropped by 0.7mm to give squish of 1.8mm, same as red line in first graph
BLUE line is same as blue line in first graph... cylinder lowered but then exhaust raised a bit
Doing the squish by machining the head shows a small gain everywhere without a loss of top end
Oh well at least that is how they feel to ride.. . . , but basically the 300 is set up for low down and looks easy to get more top from without losing much bottom end, while the 250 is already biased towards top so trying to get more comes at a cost. . . ...
Sure, figured you had the barrel done up. I was meaning Lonetree seemed to be doing addition using measurements of gaskets in free air vs bolted down measurements of piston position. - At least I think that is what was being suggested, I didn't draw a picture & get the calculator out.F5, When I took the measurements for the squish samples I used the same 0.5mm gaskets from when I pulled the 300 top end off so they had been compressed, and a fresh 0.3mm as the old one tore. Shouldn't be too much difference once the new gaskets are torqued up after the work. . .
Sure, figured you had the barrel done up. I was meaning Lonetree seemed to be doing addition using measurements of gaskets in free air vs bolted down measurements of piston position. - At least I think that is what was being suggested, I didn't draw a picture & get the calculator out.
Mainly because I'm lazy.
I find that is a policy that has served me well. And will continue to serve. Unless it seems like too much effort at the time, or I just can't be bothered.
Finished the head and sent it off to jake yesterday, thought I'd post up some pics...
The finished product... Letf the squish band and gasket surface alone, just machined extra volume into the dome... Kept the standard roof height, just made it flatter and wider... Old head vol was 17.5cc new head vol 21cc, when the cyl is dropped by 0.8mm it'll give 1.25mm squish, 2 degree difference between the piston and squish band and approx 14:1 CR.
Also jake I noticed in your calculations of trapped volume you were correct up until the point where you subtracted the volume of the plug hole... It's closer to 2.5cc not 5cc, so your volume of 21cc to the top of the plug hole becomes ~18.5cc to the bottom which is about 14.5:1 CR. so the new head will be slighty lower comp than the std black insert but the better squish action will more than make up for it plus it should rev out a touch better too with lower comp.