Looking for 4-stroke power (flame on)

[C-Leigh Racing]

Stock engine with no mods except 36mm carb & pipe, compression is the key to make it grunt & pull like a 4 poke in the lower rpms.
The old H model FMF, was a good bottom end pipe or the CT midrange MX.
Compression, say around 220~230lbs & race gas to keep the piston cool, ol stock 250R will be easy to handle out in the woods with no hit surprises like jumping on the pipe.
You take low compression type, you got to rev the engine to make HP & make it pull, so what happens when you got a high revving engine out in the woods, look out tree cause here I come. Lets see how much bark I can knock off with a front wheel or a arm.

Compression, you'll find is most always the key to a good pulling easy to handle 250R engine.
Neil

[wilkin250r]

Neil, I agree completely.  I think a boost in compression would give me a good boost in low-end power.  But in the interest of cost and simplicity, I'm going to keep this motor low-compression.  This is going to be my trail bike, and pump gas gives me the ability to only carry around a few ounces of premix oil and get gas wherever I can.  Quite a few of my regular trail rides involve gassing up in the next town before riding back.

It's looking more and more like the TRX-7 is going to be my pipe.

[C-Leigh Racing]

I just dont know what I'm going to do with you guys & pump gas.
I wish there was some way, all of you could have seen the damage I have seen, that ethanol laced gas is doing to small engines. Mostly 2 strokes where the most damage is taking place, but any small type engine that has ran for awhile & then sat for a short spell, you'll end up having some sort of fuel related problem.
Theres a big push across the US right now to do away with it & many MFGs of small engines are voiding warrantys if the engine comes back in for a claim & is a fuel related issue.
We need to either use straight gas or either straight alky, but not a mix of any kind.
Most folks know all you have to do when using alky fuel, how much trouble it is to keep it from corroding up the system when the engines not in use. With the ethanol gas, nobody thinks about those issues, but that alky is there.
All I can do is try & get the message out there, the damage it can & will cause, so I'm just doing my part to try & make 2 strokes last longer.

That TRX7, I believe will be real close to the same as the CT midrange mx.
Neil

[wilkin250r]

Neil, I agree with you on ethanol.  We used to have one small station that was ethanol-free.  It was the most expensive station around, but worth it.  That changed about a year ago, now the closest is about 400 miles.

I can put race gas in at home, but this particular build HAS to be pump-gas capable, for the type of riding I plan for it.  So let's throw the hypothetical question out there:  Would you rather run pump gas, or sell your quad?  That really is the choice I'm facing for this particular engine package.

[sangheraent]

I have personally always wanted a lot of torque and built my bike to be that way. My bike is a torque monster I can still get more torque out of it but I have to give up top and mid for that.

my bike is a 4 mill 310 with a pwk39 sparks pipe 100LL fuel VF2 reeds, 98 cr250 ign. I can get a lot more torque with a 38 but I lose like 10% up top. I have both carbs and have done side by side comparisons on my motor.

[C-Leigh Racing]

What about Avgas 100LL, there an airport close by ?.
With 100 you could run around 190~200 compression but would need to stay on the jetting, be sure that engines rich.

With high compression, you can combat low octane to a point, running the engine richer than normal & at times can add a little Acetone to the gas to kill the deto.
Neil

[wretched73]

I did small engine repair for a while and I've seen the damage ethanol gas causes. especially to fuel lines and carbs it is most  apparent. And neil is spot on. None of those carb issues were covered under any warranty. That's why everything except my truck is run on av gas 100 low lead.