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here goes the 250 build

9K views 30 replies 10 participants last post by  vanillagorilla1 
#1 · (Edited)
I've been collecting the oem parts for a year now and I'm tired of tripping over boxes of engine parts in my shop. So I'm going to get moving a little more on this project. I still have a lot more work to do and am still incredibly busy with life so I wont be making much faster progress than I have been but Id like to document it for those who'd like to know. I have a running 225 6 speed high compression motor that ive been running for a few years and over 10k miles. It went so well that I thought I'd give it another go. SO here are some specs on what I have and ill continue to update as I can.

-96 xt225 short block. eBay motor of unknown mileage, but I don't care cause its getting all new bearings ect
-machined tw output shaft
-tw cylinder head
-xt stainless head pipe

items i need
-starter


First things first and thats to get the sleeve, piston, rings, crank rebuild parts, valves, springs, valve seals and send them off. once thats back to me ill have the case machined for the 74mm sleeve and build the bottom end.
 
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#6 ·
I be following !!


Sebastians info says it works and is 16mm, I am still looking for a resleeving service, before I commit to piston as well I'd prefer 9.5 to 1 at 250cc rather than 10.25 to 1 at 226 and that is basically the difference. I guess shipping it all is no big deal as I just cam to me in the perfect box !!
 
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#7 ·
im going off sebastians info as well. he helped me the last go around with my 225.

heres a link to the guy that rebuilt my crank, honed the cylinder, and re cut the valves last time. I will be contacting him shortly when I get a cylinder and my sleeve shows up. he does excellent work
Home Page
 
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#8 ·
I got him bookmarked as well. He has a few youtube videos that are confidence inspiring in his work, maybe we can get the timing perfect and have him do 2 at once, this is my main interest. I got a like new ttr230 cylinder that is runable as is at 70 or perfect for 71 but I got a few yfm/yfb cylinders tagged on ebay in the $30's that would be perfect for the 74mm conversion. I was gonna call la-sleeve tomorrow too since I saw on their site they do in house sleeve work in their shop.
 
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#9 ·
i figure im a few weeks from having parts to send him. ill probably call his week. im just gonna ebay a junk ttr225 cylinder.
 
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#11 ·
I spoke with ken yesterday and the consensus is to bore and sleeve the ttr cylinder to 74mm. I have a la sleeve 74mm to have installed and I ordered the xt250 piston as well. Aiming my compression at 9.5:1 for now but may end up stroking the crank later and that will raise the compression waaaaaaay up at that point I will have to grind on the head to reduce it, but thats another process. Once I have parts in hand I will update this again.
 
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#12 ·
I think that is the best combination all around. I just got my mill set in place today and picking out a boring head suited to do this myself. In fact I just came back in from the shop studying my $11 nasty 225 test bore cylinder. looks like I will be behind you a bit as I have not ordered a piston or rings yet.
 
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#13 ·
It’s gonna be a while. The piston was a backorder so a couple weeks and the Ken said he’s three weeks out. All the head work will take time as well. I haven’t a clue!!!
 
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#14 ·
to my surprise I stuck this in the oven at 450 for 5 min and the sleeve just fell out. after further measuring with the 225 sleeve in my hands the raptor 250 sleeve should fit just fine. Still waiting for the piston and then it all goes to the machine shop
Untitled by dolphaxel, on Flickr
 
#16 ·
#17 ·
If you are using the piston I think you are, I believe the cr will be quite low. Like way below 9.5:1 low. The details are a little fuzzy to me but it might be worth checking out my "let's talk compression ratios" thread. That is where I did all the measuring, etc.
 
#18 ·
Hmm. I’ll look not it more. If it looks like it’s dropping way low I may be able to bring it up again by moving forward with a stroked crank, but I hope that’s not the case. You’re correct. It’s the pre 13 xt piston. I’m also hoping I don’t have interference with the piston skirt but I need to open the case mouth yet to check on that.
 
#20 ·
been over a year since anything happened with this, but the case has been with a machinist friend to open it up for the 74mm sleeve. just a quick test fit here. the sleeve is slightly longer and I was worried it would collide with the webs of the crank. I was sure wrong however and they're no where close to having an issue. next step is to order some gaskets and do a test fit and calculate compression ratio. Im thinking its going to be off from what I want so I will adjust accordingly. If low I will send the crank and have it stroked till the ratio is right. probably take another year at this rate to do anything about it, but its on my brain.

Untitled by dolphaxel, on Flickr
 
#21 ·
this dude takes up aaaalllllll the tw time and any other time for that matter. the jeep was purchased as the family tw for the coming years.

Untitled by dolphaxel, on Flickr

Untitled by dolphaxel, on Flickr
 
#22 ·
a few updates to post. first off I finally got around to installing the tar stainless pipe with the bung I welded in for the Wideband. It will not be a permanent thing but I'm going to see how to use it with the 225 and when the 250 is done I should have an easier time tuning it.
Untitled by dolphaxel, on Flickr
hard to see here but the o2 sensor is there under the carb tucked away
Untitled by dolphaxel, on Flickr
 
#23 ·
next was the dry fit of the 250 parts now that the case is bored. Im waiting on the base and head gasket so I can do a proper compression ratio calculation. I will adjust accordingly once I know the truth.
Untitled by dolphaxel, on Flickr
Untitled by dolphaxel, on Flickr

here is a short of the LA sleeve invoice if anyone want the number for the sleeve and what the job cost. Bottom line here is if you wanna go fast it always takes some bucks.
Untitled by dolphaxel, on Flickr
 
#24 ·
I'm about to add an O2 sensor on mine (temporary to get it tuned in slightly on the rich side), and I really love your setup! The dash setup is awesome and the sensor placement is well thought out. I noticed you put an oil pressure switch/transducer? on the plug on the head. Curious what the part number for this is? Love this thread.

:hatsoff:
 
#25 ·
im pulling this out of the history books, but the sensor was from a 2000ish kawi voyager. the harder part was finding an m6 to 1/8npt thread adapter. I also will tell ya that these engines make hardly any oil pressure especially that far down the line. its only enough to turn the light off at a dead cold start. as soon as the oil warms any the light stays on. I put a switch in line so I could turn it off. I really only wanted it when I started it up and when I changed the oil. If you find one that works better share it with the world.
 
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#28 ·
Maybe I shouldn’t put this in public, but bicycles are my #1 hobby. A good friend is a custom frame builder and he just did it real quick free of charge. Took 5 minutes. I always chuckle at motorcycles cause the frames are garbage compared to a bicycle of quality.
 
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