As far as i know, Matt (MHR) is the only one doing a 310 kit.  LRD used to do them back in the day and im sure he would do one again for the right price.

LT250r's are under rated.  They can be built up to make good power comparable to a trx.  Front clips can be changed to handle as good as a new bike.  They are everywhere and you can find them at a low price.  87-92, are the years you want, avoid the 85-86 as the aftermarket parts just arent there. 

My .02

I have 2 big bore 250 engines. The first one I had Trinity do way back when. It was quick but nothing compared to The new one Carl (iceracer) built. Its 285cc with a sleeve thick enough to be punch out to around 310. Id go more into whats going on inside of it, But I'll leave that to Carl.

I want to do another LT250. I miss my 87 that I had. The Zilla is awesome but it is a brutal beast. I loved the zip of a strong 250. 

you want good or the best?   Best Shearer pipe, Vforce reeds and a TM 38 or pwk 39 carb.   good Paul turner pipe same reeds and carb s

i think the lt250 is under rated bc you dont see to many and the few that i see arent well built  and can barely hang with a stock 450 4 stroke.  they can be built to make some good hp  and i agree with ice racer, big carb, v force reeds, shearer pipe will run really good.

I have a setup for the 250 that should make it really run. The Bigbore is done and in Gilles bike, his is a 285 and can go to a 301.
I am working on a stroked big bore that should make for a more mild power curve. Its in the final stage of R&D.  Stroking a 250 creates some issues that need to be adressed I have been working on this when I get time for over a year to get it rite.  When I get it all done It will start as a 293 or 301.

Carl, what year model for these kits, looking for 87 and up? Or is just easier to just get Jr a another LT500 for the money?

We found a 91 LT250r / waiting on someone with a 87-LT500 and 85-LT250 for sale

Joe says that your 250's scream, and I believe him. See what happens, sent you the links on the Quads I am looking at.

Trying to go out today or Sunday, the LT250 in the deal is a 85, what the hey can we do to that? is it worth it? the 87 LT500 seems to be the deal.
Plus I am waiting for some el casho dernaro to arrive today.

Mostly the aftermarket. But the stock cylinder layout severly limits what can be done. And lastly money you can build a Honda for 1/3 the cost of a Suzuki just because of the aftermarket support. Everything we do is semi unique, We use as many off the shelf parts as we can. Ive even gone so far as to try other cylinders for the 250 but its so much work its not worth the aggrivation.

Reason, Cost , the cost to design the top end, then the mold cost, think there is just too much out of pocket cost, say easy to spend 15k to just get started, then ask the questions, how many would iI be able to sell? Will the cost be too high for the average wallet? I am guessing easy $1250 $1500 for 320- 330 kit, then cost of machining, and having rods made for the kit, then the testing of the top end to see how it works, then the cost of fixing any defects, you guys complain on the cost of a LT500 pipe, think your money ahead to stick a lt500 engine in a 250 frame or 450 frame, than trying to rebuild the wheel.
Still think if one of you guys got it together on the 450 frame hybrids you see more jump ship in that direction, newer geometry, more plastic choices, many a arms and shock components available, plus it would be light weight bas azz toy.

What about designing a new top end from scratch. Head, cyclinder, etc? Do you have to be a physicist to create it? I'm no super mechanic, and I don't know that much about engine dynamics.  However some of the things these builders say on here, make me think they probably could.  That's my 

The molds and core boxes for manufacturing are very expensive. Loren Duncan said that it cost him almost 100Kby the time his 250 Honda cylinders were ready for market.  First iteration molds are typically around $30.000.  Testing for reliability and power should be a priority of a company that produces after market products.  Many design refinements and modifications and or new molds are usually required before you have something you want to sell the public.  I think that most of the aftermarket companies do not do sufficient testing before releasing their cylinders and cases for sale to the public.   Ask Eddie Sanders about the problems that are surfacing with their new Honda cases and cylinder kits.  Look at the new prices of the ESR engine cases, they have almost doubled.   Look at the new prices of the new ESR cylinder kits.  I think that he is having to pass on the cost of more testing and refinement that should have been done before putting these items up for sale and or the market is not as large as he anticipated. 


The tooling cost has to be factored into the cost of each retail item.  If there is market for only 100 cylinders and tooling cost is 100K, then 1000.00 has to be added to the manufacturing cost of each cylinder.  If there is market for 1000 cylinders and tooling cost is 100K, then 100.00 has to be added to the manufacturing cost of each cylinder.

Let have a show of hands from the guys that would be willing to pay 1000.00 to 1500.00 for a cylinder and head kit for a LT 250 or a LT500. 

Oh what size LT500 jug? 650cc- 685cc, heck Im in!!