125-200cc E.g. 144 Race Fuel Question.

Hey all, I'm on the edge of purchasing a beautiful 2008 cr125 with the E.G. 144 kit from a very good friend but I don't want to run race fuel.. We don't know if the bike has the pump gas or race gas mods to the head..... The guy who sold it to my buddy was using 50/50 pump/race (which doesn't mean much), and my friend continued to use it to be safe.. Here's a cooky question, does anyone have the compression figures (static - as in pounds measured with a good old fashioned tester) with and without the head mods.. Or even an approximation of the origional compression (if it's allot higher then I'll know LOL)..

I figured that I could send the head to E.G. to return to pump gas but I've read that some people couldn't even run the E.G. pump gas head without at least 50/50.. If that's the case lemme know.

Also since I'm picking your brains.. Does anyone know the original rear spring rate for the OHLINS shock in '08... I'm of the larger variety LOL and I can get .48 fronts from Enduro Engineering (which is what I need for 235 lb Vet).. But I'm lost on the rear.. I'll do the springs now and have it valved later..

Thanks in advance,
Glen.

Mixing a little race fuel isn't so bad. In general and there are many variables so there is no one answer but if you cranking compression is around 200 psi or more it's a good bet that you will have to run race fuel. (or at least a mix of race fuel)

My stock 09 WR250 needs a race fuel mix at the least but my 03 GasGas EC200 will run on about anything.

We checked the compression today (after a bout 1/2 hour on a fresh rebuild) and it's at 205 psi.. So it appears I should run a mix for now (I also found out the standard comp should be around 175 - elsewhere in this forum)... I'll probably run a mix for now and send the head out to E.G. during the winter for pump gas mods..

I can figure the new rear spring rate, but just needed to know the original rate for the Ohlins shock..

It is very easy to change you compression downward. What width base gasket are you currently using? You should drop about 5-7 psi for every .1mm. Also if you feel that your best route is to have your head machined for lower compression of about ~175 psi, I can't imagine that you can't get that done locally. You need to do a solder test for your squish band gap. Go to RB Design's web site for the proper method and test. I would send my head to them if you want an expert in 2T heads to do your work before I would send it to EG and get into his que of many. You also might try to find a stock 125 head on fleabay and just have the squish band widened to 58mm diameter. You will definitely be in pump gas range that way even if your squish isn't ideal. Just some thoughts.

Thanks for the good ideas, I might look into the 125 head (I work in a machine shop and can modify to the 58mm dia. - in fact I could probably do the work on the one I have LOL).. I don't wanna run the thicker gasket as I don't want to change the port timing..

I didn't think I would want to run race fuel either but once you get used to how sweet and crisp you can get it tuned you may start liking it like I do, not to mention how crappy pump gas is especially when it is ethanol mixed.

I weigh 185lbs naked and use a .40kg fork spring with perfect sag numbers. .48kg will be extremely heavy for even a 235lb rider. What are your sag numbers ? What type of racing are you doing ? I am also running a 6kg shock spring with perfect numbers. I even let Drew Smith of Works Enduro Rider, ride mine at the last Nat'l Enduro and he thought my suspension worked well. He thought my suspension not only worked well be was plush. I had about 20% of the compression taken out new. When I get my shock serviced I plan on having another 5% taken out of shock compression. I am all the way out on my high speed damping now. I use a blend of 2 gallons of 110 Sunoco race gas with 3 gallons of 100/110LL AvGas. PLUS, 1oz of Startron fuel additive.

I'm racing motocross mid pack intermediate on an RM250 right now, I run .50's front and a 5.4 rear on the RM (the shock spring difference from the RM to Husky lies in the linkage ratio), And I've always run .48's on my old 125's - the figures I use come from the race tech website calculator which has worked well for me since about 1999... If I was to race hare scrambles I would definitely run much lighter springs to avoid deflection and such, but I'm all about coming up short on a 30' double and carrying on racing with a story to tell - and it's gotta be stiff for that.. LOL.
I believe I will likely stick with the head work on this bike (you guys talked me into it) as it is jetted so clean and runs absolutely perfect and I would hate to mess with it..

Still curious on the original spring rate for the 2008 cr125 it would be the same for the sachs or the ohlins as the linkage was the same.... I believe they changed the linkage in '09 & up..

Thanks again for all the info. guys!! I think this bike might slow me down a little off the start but I believe I can run a little harder a little longer on this bike (I'm hoping to make up time on the last couple laps), and i'm just in it for fun now teaching my son the moves on his KX65... I'll let him do the fast stuff for both of us later!!

My 5.6 spring came off a GasGas Sachs shock and is longer but still fits on the Husky shock.. Would this affect sag? It worked out for me but you are lighter than me and your spring is stiffer so I'm just wondering how that might have worked out.

Also do you know what the fork spring rate is in the stock 09 WR250. At first it felt way too stiff for me but once I got the rear set right the front evened out nicely (after the above mentioned work).

Lastly, why mix AV100/110 with 110 Sonoco? Is that for money savings or performance? I was using 110 Sonoco in NE OK ($9 per gal) but here in MO I was planning to use VP 110 ($8 per gal), it would cost me more to drive from where I buy VP to an airport than what I would most likely save. lol

Thanks for your help, I find your posts very informative.

As for the gas, your bike really doesn't need race gas but we can hardly find decent 93oct without ethanol. The Race gas gives the AvGas some of the kick that AvGas doesn't normally have. Throttle response suffers with straight AvGas . But we don't need 110 octane. Too much octane actually hurts performance.
Next the spring rate ALWAYS effects sag. I haven't a clue what a 2009 Husky has in the forks. Mine came with.42 which was too stiff for a 125 type bike with someone of my weight. I am not a lightweight. I ran .42kg in my 525EXC KTM. .44kg was too stiff. Worked well in whoops but turned like crap. On my WR150 I had to go down on size in front and up 5 sizes on rear. Jay Hall weighs 215lbs and uses a 6.8kg on his. That sounds to me a bit heavy but the trick is to set your static sag to about 33mm and see what your rider sag is. If your rider sag is 98-105mm then you are in the ball park.

Matt,

I wouldn't mind having that head if Glen wants to keep his as a higher compression motor. My spare head is sitting on a top end in Pennsylvania for a back up top end for a young racer.

Walt

Yeah i think I'll stick with the higher compression so you guys can figure something out.. Thanks very much though!!

I have a EG 144 with a "pump gas" and I have to run 50/50 powermist T-111 super high octane.

I ran 1/3 race gas at the Speedsville sunday and it was pinging again.

Retard the timing one degree and run pump fuel. This is what I do on my high compression yz motor cause I'm too cheap for race fuel or to buy a new head.

X2 for RB designs. Ron is a magician when it comes to 2 strokes.
I've seen him do his thing many times and the $75 he charges is a bargain for the effort he puts in.

So I should send my head to RB Designs?

I guess I need to pull the flywheel to retard the timing?

You can do it with the flywheel on

thanks! I'll check it out.

On a WR too? It has a bigger flywheel.

We were talking CR