Author Topic: top end rebuild (Read 1313 times)

Weasel77 · « **on:** March 29, 2015, 05:11:04 pm »

Hello, new to this board. I have a 88 lt250r. I recently cold seized it. I took it apart and took it into local shop. They honed the cyl. ( did not bore it) and took down the sizes for me and ordered a new wiseco piston. I put it all back together and got it running was in the process of breaking it in ( 20 min). When it just stopped running and now it wont start. I have good spark and have tried replacing the plug and nothing. it backfired a couple of times. Havent done a compression check yet, but it does seem to kick over easier than i remember. Cylinder is from lrd its shaved and ported and polished with a spacer at the base. Stock head from what i can tell. Any help would be great.

Gillio · « **Reply #1 on:** March 29, 2015, 06:41:17 pm »

Welcome, And a look at the reeds may be in order.

Weasel77 · « **Reply #2 on:** March 29, 2015, 07:04:31 pm »

reed cage is brand new also brand new k&n filter without box

Gillio · « **Reply #3 on:** March 29, 2015, 07:12:28 pm »

well then id look at the flywheel keyway. It may have sheared. It will have spark, but not properly timed spark.

GrkGuy · « **Reply #4 on:** March 30, 2015, 03:59:39 pm »

Check ground.and if it back fired you could have broke a reed.

Weasel77 · « **Reply #5 on:** March 31, 2015, 03:56:43 pm »

ground was ok and flywheel key is ok. so i took the reed cage out. and there is two pieces. i took the screws out ,took 1 piece of plastic off then took the reed off in the middle of the bottom edge its burnt black like half way threw , this isnt normal right.. could this be from when i cold siezed. also checked compression could only get 65 could bad reeds cause low compression since its a new top end?

Quadster · « **Reply #6 on:** March 31, 2015, 05:23:06 pm »

Its always best to have the cylinder bored/honed to the piston. Pistons can vary in size.

Weasel77 · « **Reply #7 on:** March 31, 2015, 05:39:43 pm »

I did. The shop that honed it also ordered the piston set. Would bad reeds give low compression

Dutch_Rutter · « **Reply #8 on:** March 31, 2015, 10:04:30 pm »

If they are bad it should not cause low compression, bad performance once running yes.

GrkGuy · « **Reply #9 on:** April 01, 2015, 09:22:58 am »

Got any pics of the reeds, But sounds like you will need some new petals, how did the reed cage look where the reeds sit in it at. Was the ends melted on the plastic cage. This will get burnt sometimes and then you will need a new cage also.

LT500Kid · « **Reply #10 on:** April 01, 2015, 10:04:25 am »

65 lbs is extremely low compression

Q2W · « **Reply #11 on:** April 01, 2015, 03:06:16 pm »

Did you hold the throttle wide open when doing the compression test? Be sure to kick it like it owes you money and knocked up your sister.

Dutch_Rutter · « **Reply #12 on:** April 01, 2015, 08:59:25 pm »

^This

If you end up getting another super low number I would be pulling the head and cylinder off. Sounds a bit like my 85 motor when it was trying to seize because the wrist pin came loose, and dug into the side of my cylinder.

Weasel77 · « **Reply #13 on:** April 02, 2015, 02:36:10 pm »

I didn't hold throttle wide open when I checked compression. Does this really make a difference, since I heard you can check compression with carb. off. Also I tried loading pics of reeds, but it wouldn't let me. My reed cage is not plastic it is all metal. I have a extra set of boysen reeds that I'm going to try. I am also doing a complete cleaning of carb since it's been sitting.

Weasel77 · « **Reply #14 on:** April 03, 2015, 06:14:02 pm »

well I figured out the problem. I took the cyl off again and the rings were seized on the exhaust side. pissed off I only ran it for 20 min. I did notice that the crank had some play in it. So I took the flywheel and stator off. The crank moves back and forth and a little up and down. So then I drained the oil ,only to find shavings in the oil. I took the clutch cover off and noticed that one of the ears on the crank that runs the water pump is broke off, although my old motor was like this too and it didn't affect it. I took clutch basket off and there is what I feel a lot of play in the bearing the crank comes threw. I think this was my orginal problem. It just pisses me off when I bought this motor it was suppose to have been totally redone. It only had like 5 hr on it. So I guess I'll have to either buy a new motor or try and rebuild this one. Any advice on the rebuild or different motor. or anyone that would rebuild it and how much they charge.

Dutch_Rutter · « **Reply #15 on:** April 03, 2015, 08:49:40 pm »

Sorry to hear that. There are a lot of guys on here who can help out with a rebuild. I had my machine work done by Jerry Hall of Halls Precision Racing. and did the rest myself. If you can find a good deal on a motor pick it up but I have always been cautious about that because you might get the same exact half ass rebuild job. That is how my 85 motor was... "rebuilt" I only buy a used motor with the intention to rebuild it again. You will probably be better off getting your rebuilt but it is definitely not inexpensive. Good luck though

Patman13mia · « **Reply #16 on:** April 04, 2015, 10:32:35 am »

Drom buying more than a few bikes in my life ive figured out that even if it says its been rebuilt that dont mean anything!! EVERYBODY says a bike has been rebuilt but did they really put it together correctly? Did they replace every bearibg seal and crank?? Idk bout you guys and the inexpensive part but i just rebuilt top and bottom and im past a grand and not even done!! Now thats ith extensive port ork and every brand new piece!! But that is a complete rebuild unlike majority of these craigslist bikes that you find around. Building them right takes time and money. It would be dumb to do total rebuild on these bikes then sell for 1,000 dollars.. So never believe what you read/hear until you open up that bottom end my man!!

Weasel77 · « **Reply #17 on:** April 04, 2015, 07:25:54 pm »

so I pulled the cases apart and when I took the crank out the bearing on the right side just fell out of the case. all in one piece. I thought these were suppose to be pressed in and it was very sloppy . a lot of play. is this suppose to be like this. if not is my case shot or can I put some kinda sleeve in it at a local shop? thanks for all the help. also I found the piece of the crank ear that runs the water pump. in the tranny.

Dutch_Rutter · « **Reply #18 on:** April 05, 2015, 01:08:21 am »

Sounds like your in the same boat as I was. The bearings should be pressed into your case halves. If they do not fit in there tight enough without play then your case halves need to have inserts made for them that will fit your bearing properly. Once again I had Jerry Hall do mine for me. He did a great job on them. If you have those done you might as well have the sealing surfaces checked out as well, They may need some machine work to ensure they are flat and fit together just right.

Quadster · « **Reply #19 on:** April 05, 2015, 09:59:35 am »

Whats the going rate now for inserts? Last ones I had done about 4 or 5 years ago on a zilla motor were about $300 with bearings.
If you go the insert route, have someone do it that has done them before. Your local machine shop more than likely has never done them before.

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Author Topic: top end rebuild (Read 1313 times)

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