Posts
28
Joined
1/16/2016
Location
North Canton, OH
US
nkoebes826
8/3/2018 10:53am
8/3/2018 10:53am
Edited Date/Time
9/22/2018 8:35am
Over the winter I had my cylinder related and matched to a standard bore pro x piston on my 1998 KX250. I assembled everything coating the piston, wristpin bearing and cylinder in HP2.I fired the bike up and did a heat cycle on it and everything seemed to go great. I went to start it the other day and it seemed like the motor was locked up. the kicker wouldnt move. It finally ended up breaking free. Instantly before I did anything else I pulled the pipe off to look in the exaust port and the cylinder walls looked fine but the piston not so much. Im 100% sure I had 32:1 fuel in it and my radiator is still full of coolant. Any help or ideas on what may have happened would be appreciated.
I wouldn't worry too much and just try to run it. Pull the air filter and look down the air boot first... Just my 2 cents.
Paw Paw
The Shop
Paw Paw
if that was a new plug and it only has an hour on it or less, you have other problems. might have a bad crank seal. you should pressure test the engine.
I pulled the bike apart today and heres some more photos. Like I said the piston has roughly 6 minutes on it. Also I should have mentioned the spark plug was not brand new. It had a few hours on it. I really appreciate the input from you guys.
Nathan, get a measurement of the bore, piston, and post them up here. Also, post a photo of the bike so it gets some love and there is an understanding of its cleanliness and state of being.
Heres a few photos of the bike. Like SLOWTIME said its an extremly clean and well taken care of Pro Circuit Splitfire bike ive been slowly building. Ill get some measurements of the bore and let you guys know. I dont have a bore gauge big enough for the cylinder, just a set of micrometers. If anyone knows a better way to measure the bore let me know.
Pit Row
take a piece of notebook paper 2" long and 1/4" wide then fold it over the bottom of the cylinder so 1" of it is in the cylinder then install the piston from the bottom and try to push it past the paper. tell us if it takes light force or moderate force or if it is too tight to push past it with moderate force.
I'm assuming you have a 2.1mm oversize piston. I thought they did .04 inches or 1mm increments but I guess there's more options than that. (I've been researching as I type this. Lol.) Did you measure the piston on the lower front and back of the skirt? A 68.5mm piston should measure 2.694ish inches. That would be .0025-.0030 inches under the advertised size to make up for cylinder wall clearance. Your numbers are exactly 68.5mm. Unless, your plater made the cylinder bigger to add the clearance. That doesn't sound right to me though. And again based on your numbers, that's too much clearance.
This is all interesting to me and want to learn as well. Let us know what you find out.
Your clearance thoughts are right on. I am not trying to hack this thread or sell anything yet plan to add a positive experience to restorers. I am 59 and have owned 48 bikes since 12.
My local ATL shops require $125 to bore a cylinder. Outrageous. I have located an EBAY machinist that I have had bore 2 vintage cylinders for 49.99 plus shipping.
Suzuki_star_racer
Steves Cycle
641 Centennial Rd
Rutherfordton, NC 28139
I talked to him before shipping and I have the shop tools to confirm the returned borings are within 0.0002".
My experience is good........
Just a viable thought guys.
You can also use narrow feeler gauges but they are getting hard to find.
Post a reply to: Read this KX250 Piston