Mc300

[widebear]

Has anybody swapped a 300 top end on to a mc bottom end. I,m not really a big fan of my 300 ,even with the smaller ign and other mods it still does'nt have enough over rev for my liking and I much prefer my mc250. So I'm curious as to what kind of a mix the 300 top end and lighter crank of the mc would end up like. Other mods on the 300 are Motowest pipe. delete reed spacer and head mod. I'm also thinking that an other .5mm base gasket might help move the power up a bit.

 

[Loosenut]

Is it an EC or XC head. My '05 with the stock EC head was rev'er.

 

[widebear]

started out as an ec head then modified to RBD specs

 

[GMP]

The lower ends are the same with the exception of the primary counterweight being absent on the MC, which has a small spacer. Slightly less flywheel effect, thats all.

The gasket may do a little but all your precision head work is out the window then. Retard the timing a bit and/or try a GG or Doma pipe.

 

[widebear]

Ive tried a few pipes on the bike including the Doma.I guess i'll try running the timing at half a degree btdc with a xtra base gasket.I did like the off idle pull with the head mod but found the bike more difficult to start after a stall, kinda like a real open bike.I would like to know who has the lightest piston , I'm guessing a vertex. Maybee we need to start a facts and questions thread to address these kind of things.

 

[GMP]

When you had your head done, did you retain the stock compression?

 

[widebear]

The compression was not corrected back to stock ec spec, have to check my notes but i think 15 psi higher.

 

[GMP]

Wow, that might explain things. Ron told me 200 PSI tops for pump gas. I was 195-200 on my '03. The '07 with .3mm and .5mm gaskets, stock head, runs 185 PSI on the same gauge and revs like a weedwacker. It pulls off idle good so all I would do is correct the squish.

 

[widebear]

Glen. So I looked at me records.They show a starting comp of 150 psi at sea level with a revised reading of 175 after cutting, this was quantified on two seperate guages.I think we may have inadvertently discovered why Canadian and U.S. market bikes respond differently to L.T. jetting?

 

[iancp5]

Glen. So I looked at me records.They show a starting comp of 150 psi at sea level with a revised reading of 175 after cutting, this was quantified on two seperate guages.I think we may have inadvertently discovered why Canadian and U.S. market bikes respond differently to L.T. jetting?

I'd be surprised if they were different other than by gaskets. I guess the MC might be different to EC but not in different countrys. I suspect GasGas aren't big enough to manufacture many different parts. I bet the difference in jetting between US and Europe is down to environmentals and terrain. Speaking for the UK we are more focussed on slow terrain. I know US and Canada must have some very technical stuff but some of you are running more European jetting so I guess the others are more into high speed open stuff. A lot of you go for more MX like bikes and want an exciting hit. In the UK there is more a tendency to go the other way. Possibly because the whole of the UK gets lots of rain.

Has anyone compared part no.s that'll confirm.

 

[GMP]

I know the MC250 head is different, but thought that all 300s had the same head (by part#s anyway). The best way would be to have the head "scooped out" a little more to drop the comp a bit. Maybe find a spare head on ebay and have it done that way(with less compression).

Jetting response may have something to do with the CDI as well. A lot of the older XC300s ran 250 CDIs, and XC250s 200 CDIs. I know because I had an '00 XC250 and used that CDI in my '03 EC250 for big gains in low/mid. Cruiser did the same thing with the same results. Now, are the newer US DEs the same as the ECs ?

 

[iancp5]

Last time I looked at the parts book for the later bikes CDI was the same for 200 - 300 regardless of EC, MC or SM. But maybe they are switchable? That would be good - maybe you can have more than a wet & dry setting?

 

[widebear]

I dont put to much stock into gasgas part#'s, you can have 3 different kick starters all using the same part number.I,m going to make note of the base gskt combo to compare with other 300's

 

[GMP]

Good point there.

The CDIs had different color shrink wrap on the harness starting in '01 to differentiate the maps:

125 - yellow
200 - blue
250 - red
300 - black

Prior to '01 all were black but there were different maps.