Has anyone had good luck with these
kits racing XC? I have a 86 250r with a
adjustable LRD pipe along with other
small mods. Thanks for info

 

Don't waste your money on a 310. They are actually 295 kits. I think the biggest they get after overbores is 303. If you have a stock 86 cylinder, bore it to 69mm then you will have a 270R that is big enough for xc racing. You need bottom end so get some head work and some mild porting to keep the power in the low RPM's. Actually, you could do your own engine work. Get a 1996 CR250R headgasket and widen your exhaust ports a little bit with a dremel or die grinder. You will get tons of bottom end and it will rev quickly. I did this to my dad's 86 and the compression is high enough that we have to get stiffer springs just to keep the pipe from expanding. If you want a great XC motor do this.
Along with what I said above a Bills pipe, fmf silencer, stock 34mm carb, K&N filter and either 12/39 or 12/38 gearing. Get the jetting setup correctly and you will have a sweet R motor. I used this same set up for MX and I got the holeshot on everyone, including A-class riders. They couldn't believe I had no porting done.

 

Please correct me if I'm wrong, but isn't there a difference between the 295 and the 310 kit?

 

I'd have to say leave porting to the experts...just 'hogging' out your ports will most likely lead to a bad experience

 

One of the advantages of the 310 kit is the custom cast cylinders superior design. The ports are more favorable(They actually contain two extra ports) and the cooling jackets are increased. The power gains are incredible on this setup. I personly feel it is too much hp for xc, and more suited for mx or tt. The 270 is plenty enough motor for xc or even just the 250 ported. Dont port yourself, you cna get lucky or you could buy a new cylinder.

 

As far as the 310 kit and the 295 kit they are actually the same size kit. The 310 is just a new cylinder while the 295 is a new sleeve. You can verify this by going to the CT website and checking out the pistons. You will see that the 310 pistons are 72 mm stock. Taking that info you can find the actual displacement of the 310 kit by taking this info into a calculator (7.2cm/2)^2*3.14*7.2 this equation is actually less than 295. That is the displacement you have with a 310 kit. The reason being is that you can't go much bigger on the bore without machining the cases of your R. The porting on the 310 is better and you can get them nikasiled which never has to be bored you just replace the piston and rings. However, for XC racing you would probably be much happier with a ported 250 cylinder. If you want a little more then go with the 270. Just remember that you only can do that with an 86 cylinder. Also remember that with a 69 mm bore that you would use with the 270 motor, you really need to keep the piston and rings fresh so that you don't have to have the cylinder bored. You are on the last overbore with the 270 so the next thing you get is a resleeve. Hey perfect time to get a 295 sleeve installed. That way you are used to the big bore power and you can keep your stock sleeve for awhile. I have actually read that if you keep the piston and rings fresh in a 270 you can go years without a bore.

 

Hey thanks for the info guys. I forgot to tell you the bike is already bored 80 over which I believe is my last bore. I'm not sure what that makes it cc wise? I already have a stock Honda sleeve and piston that I bought last year assuming that I would need it. I think I'm going to send the top end to LRD to have them do some porting. Any suggestions on the stock sleeve or 295 kit ??????

 

Your displacement with the .080" over bore is about 261cc. If you have an 86 250R you can go to .120" over. If .080" is your last bore then you don't have an 86 cylinder. If I were you I would have LRD bore it to .120" then port it. You will have a sweet motor then.

 

Let LRD recommend a kit for you. They have more experience than all of us combined. They know exactly what will work and what will not. Personly I would never perposely bore a cylinder to its last bore. You could seize it on your very first run and then you have nothing. If you want a big bore check into the Pro X kit(310-330-350)or have your cylinder big bore sleaved. The moral of this response is LET LRD ADVISE YOU!