1991 lt250r restomod build

1991 lt250r restomod build
Posted by 250rider34 on 12 Aug, 2018 06:28
So this all began when I decided to replace my cases due to them leaking. When I bought the bike the right side case was broken and crudely “repaired” above kickstart g [ Guests cannot view attachments ] ear. Since I owned the bike it got progressively worse so I got sick of it and wanted to bring the bike back to it’s former glory. The only time I went in the engine was to do a top end a few years ago when I was in highschool. I had la sleeve bore it to 68.25 with a wossner piston and I put a 22cc coolhead on it. Before I dissembled the bike I checked the compression which was 150 psi.

#1 Reply
Posted by 250rider34 on 12 Aug, 2018 06:40
I stripped the entire bike down to bare frame. The frame had a few minor cracks that were welded over from a previous wreck I took a few years ago so I decided to gusset the whole frame just to ensure no future problems. I had about a weeks worth of every day after work making gussets and fitting them to the frame and welding them in. Very time consuming but happy with the outcome and the fame should be good for years to come. I used cereal box to make templates for every joint on the frame and number the templates and frame as I went them welded all in at once being sure not to get the frame too hot.

#2 Reply
Posted by 250rider34 on 12 Aug, 2018 06:45
As far as the motor goes that kind of turned out to be a worst case scenario. Disassembled and intake side of piston/ cylinder had wear my k&n came loose and sucked dirt I believe. No more k&n for me! The crank was nice and tight but I wasn’t going in there multiple times so I figured rebuild that with new rod kit and new crank bearings. There was a lot of metal in the bottom end and after splitting the cases I found a burned up shift fork and gears with some wear. So I found some nice cases on eBay and a used tranny. I cleaned up all my parts and made one good trans out of the two.

#3 Reply
Posted by 250rider34 on 12 Aug, 2018 06:58
At this point I contacted Carl as I was going to have him do some engine work he was busy but linked me up with dynoport in NY. Rich the owner seemed to know his stuff and we talked through what I wanted. Mx/trail port, nikasil cylinder, cut head to match port, rebuild crank, check out trans and back cut gears also I wanted as much compression as possible on pump gas. Hard to find race gas near me. So I sent him my cylinder with head, crank, and the tranny I pieced together. I sent all this in April. I was calling him probably once a week or every other week to check in he was saying he was busy with other jobs. No big deal I understand if your on another job you get that done first. ( I’m a diesel mechanic worked for caterpillar now work for the county) we’ll finally he got to it and said he needs the cases and we had some bad gears so I sent him the other trans and cases hoping the bad gear is good on that one. Now I measured all shift fork clearance and inspected all the gears before I sent him anything but I figured maybe I over looked something.

#4 Reply
Posted by 250rider34 on 12 Aug, 2018 07:06
So while the engine is away I ordered every bearing and bushing on the bike had my frame, a arms, etc powder coated by a local guy who did a good job and turnaround was only 5 days. I also ordered elka shocks through lonestar racing due to the fact I’m running their +2 + 1 a arms. I made very clear on the phone it was for a 91 and that 91-92 have a different rear shock and he said no problem. Well this was first week of may I didn’t hear a single word back until June. It was only suppose to be 2 weeks to build the shocks. Well they call back and say the front shocks are built but elka can’t make a rear shock they don’t have the parts to do so. So after all that time and they just tell me they can’t make the shock that I specially asked if they could make. Note this is not Elkas fault it is lonestar. I called elka direct which I should’ve done from the start they explain the fork on the bottom of the shock they don’t make anymore and the icing on the cake the fronts were never built. So lonestar said they will take 200 off the 1000 and I can have just the fronts or cancel the order.

#5 Reply
Posted by 250rider34 on 12 Aug, 2018 07:16
So now I’m trying to locate a rear shock. I was previously running yfz 450 fronts and a z400 rear I had the oem rear but needed rebuilt. I called race tech and they linked me up with noleen j6 in Cali. Very knowledgeable people and top quality work. I believe I spoke to Clark and he said go with the elka fronts and send him the rear he said the elkas will be great at first but I will want more as there valving is so so and to send him the fronts when I’m ready. The pricing was great I was expecting 600ish I figured I needed to rechrome the shaft. I think it came out to around half that plus shipping and very fast turnaround time took longer to ship from nj to Cali and back. The elka shocks showed up a few days before my rear from noleen.

#6 Reply
Posted by 250rider34 on 12 Aug, 2018 07:25
Now it’s end of June and I got back everything from my motor except the cylinder which was being plated at powerseal in pa. I told them expedite it as I was going to my cabin in Maine for two weeks I wanted to ride. I got it maybe a week later. Now when I opened everything up I was not a happy camper. The head was not machined and I was under the impression it had to be cut to match the port. I also wanted the head stay machined off which wasn’t done. The crank was rebuilt with a hot rods rod I wanted pro x. Trans didn’t look like anything was done except clean up the slots where the dogs engage not backcut like how I wanted. I called rich and had him explain he said head didn’t need to be cut since running pump gas he forgot about machine work ( I left detailed note of what I wanted done) trans he said he undercut the gears and he said tranny should be good to go he was confident in it. I gave him the benefit of the doubt. Now I assembled entire bottom end and was waiting for the cylinder to come. Installed pro x crank bearings and seals, winderosa gasket kit with oil seals, ebc clutch kit, rebuilt waterpump new bearings impeller seals etc.

#7 Reply
Posted by 250rider34 on 12 Aug, 2018 07:33
A few days later my cylinder came back. First thing I notice is my power valve adjuster the top bolt was stripped I wanted that repaired wasn’t done. The exhaust flange had a broken stud I had to remind him to do that luckily powerseal did it. The playing looked very nice I’ve used powerseal before with good results. Now as far as porting goes I will say 2 stroke porting is not my forte and I don’t claim to know everything but I also know good work when I see it and know sub par work. I rebuilt engines at cat so I’m fully aware of quality engine work. I do not wish to bash rich or dynoport in any way but the porting looked very unprofessional and some spots were worrysome. So I called jerry hall for a second opinion and sent pictures and we talked for quite awhile two separate occasions and he eased my mind a bit. He said don’t go by what it looks after he inspected the pictures it was crude but the basics were there. Only thing that I didn’t like was the booster ports I believe there called directly in front of reed cage were ground down to the liner in some spots and it looked like the transfers weren’t touched but hard to tell with the plating

#8 Reply
Posted by 250rider34 on 12 Aug, 2018 07:42
Well I also got the big volume pipe and silencer from dynoport that pipe looked great very happy about that. I assembled the whole bike now every bearing was replaced with all balls. Everything went together great minus the powder coat being thick causing a few minor issues but that was expected completely. I went with a new tm 38 carb using Zilla intake boots to a custom airbox and twin air foam filter. New carb the jetting was way off so I put in some starting point jets I believe 400 main 88+ zilla needle 35 pilot q8 needle jet. Got it running for a heat cycle sounded real good. But the damn clutch cover was leaking had no idea why cleaned everything torqued everything mating surfaces flat made no sense. So had to take apart my freshly painted engine to replace gasket. Overnighted one and found old gasket prefect. Installed new anyway still leaked... it was hours away from leaving for Maine now so last ditch effort I took apart cleaned everything and used the gasket with a little rtv where it was leaking at rear of engine below Kickstarter and put a little on outside of case.

#9 Reply
Posted by 250rider34 on 12 Aug, 2018 07:49
Got up to Maine put oil in it and it wasn’t leaking. So that was good. Took it for its maiden voyage and it ran good while breaking it in. After break in I gave it some more throttle and immediately knew it was lean on the main. Zero power and didn’t sound right. Also my pilot wasn’t right had to bump down to a 30. Found a dealer about 40 min away and asked what the biggest mains they have in stock were. 520,480,460 so I went and got them. Put in the 520 rich misfire so that was good but seemed real big to me. Pilot also needed leaner. So now I’m at 480 main and 25 pilot. Bike is running beautiful. Didn’t ride a whole lot in Maine also was alone my family has a 350 fourttax up there so we were just putting around basically. Clutch cover was just seeping from bottom two bolts but I said screw it next time I have cover off I think I’m gonna replace the cover as that’s the only thing it could be since it was on the old screwed up cases???

#10 Reply
Posted by 250rider34 on 12 Aug, 2018 08:01
Installed the last few finishing touches when I got home from Maine my frame guards and rear number plate retorqued motor mounts and cylinder they were all loose etc. still need to readjust camber it’s a little off. Set caster at 5* camber 4* and 1/4 toe in. Need to get better tie rods the oem style ends are junk two small or doing the bump steer mod made too much angle it looks like? Suspension works great just don’t like where my front rezzies are mounted. They were suppose to be piggyback rezzies that’s besides the point. Went on two rides so far since getting back and the bike feels great. Only complaints are shifting feels a little hard and hard to find neutral every once in a blue moon 1st gear won’t engage have to hold shifter down letting out of clutch. Also straight line drag race top end feels slow but could be porting I never use 5-6 but one of my buddies has a blaster 240 kit 38 mm carb running aviation gas few other mods honestly fastest blaster I’ve rode or seen but still a blaster lol. Also 400ex basically stock with pipe. They beat me in straight line race that seems odd losing that much top end but bottom end super responsive and I was hitting whoops 4th gear pinned blowing past them and felt faster than any bike I’ve ridden so I’m not sure what to think of it. Like I said bike runs great I believe the jetting is very close if not perfect. I need to get it on a track that will be the tell tale sign of how good it actually runs.

#11 Reply
Posted by 250rider34 on 12 Aug, 2018 08:09
I have a lot of pictures of the whole process but I can’t upload them if I can possibly send them to someone and they can post for me I’d appreciate it. I will be adding more to this as time goes on as well. I’d be happy to answer any questions or help anyone out doing similar things. I probably forgot to mention a lot of little things but once pictures are up they tell a thousand words. On a last note I plan on getting into racing depending on how much time I end up having to do so ( I work 7 days a week 80% of the time) I found a site called mxsponsor I highly recommend it you pay $50 per year and get access to hundreds of sponsors and don’t need to race. You basically make a resume add pictures videos etc and I ended up getting over 40 offers and I accepted 7 from O’Neal, twin air, dragon, factory seat covers, 4 arm strong, and eagle grit so far.

#12 Reply
Posted by Q2W on 13 Aug, 2018 11:21
Stock main for an 88+ zilla was a 350. 87 was 420 but was a bit rich.

480 for that bike sounds pig rich! No way you should be losing to a pipe 400ex in a drag race.

#13 Reply
Posted by 250rider34 on 13 Aug, 2018 18:25
Yea I was thinking that too believe me lol. I don’t have a crazy amount of time on it maybe 4-5 hours and I babied it for awhile while I was messing with the jetting. Once I put the 520 in and it rich misfired I figured the 480 should be in the ball park. The 400 main was super lean. Could it be the fact that it’s a newer style tm38 not a zilla carb? It is a genuine mikuni carb as well. It came with 230 main 22.5 pilot 389 q2 needle jet 4.0 throttle valve and 6fj41 needle. I had to take the slide out of my 90’ zilla carb as the zilla needle did not fit into the slide that came with this carb. Bike idles perfect and runs clean and crisp very good throttle response not fouling plugs still on first one. Running at basically sea level it’s been very hot and humid here mid 80s to 90s. Like I said in earlier post I’m running open custom airbox to twin air foam filter zilla boots tm38 carb v force 3 reeds dynoport mx/trail port along with their pipe/silencer, coolhead with 22cc dome, wiseco 68.25 piston. 25 pilot with air screw at 1 turn out will have to double check that. 480 main 389 q8 needle jet stock 88+ zilla needle on middle clip stock 90’ throttle valve/ slide which has no major wear in good shape. 93 octane with maxima synthetic oil. Sorry if I’m being repetitive and excessively long with the posts.

#14 Reply
Posted by El Diablo on 13 Aug, 2018 21:25
What does your spark plug look like?

#15 Reply
Posted by 250rider34 on 14 Aug, 2018 03:21
It’s a little dark around electrode but not wet at all, near bottom of porcelain looks light brown I just pulled the plug before I left for work. Although really I’ll have to put a new plug in and check again this one has been in since first startup on new engine. Hoping to get some riding in this weekend.