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Discussion Starter #1
hey all, my 250r the last time I took it out started acting up. Took it up to a retired mx track/ woodsy trail riding and was having a blast. it did seem to almost bog a little in the midrange but pick right back up on the pipe. I was running it pretty hard but stopping to take breaks and let it cool off. By the 2nd or 3rd day we were up there I was riding and it died and I could not get it to start. wait a few hours and it'll start and idle then anytime I put it in 1st and start to let the clutch out the bike dies, try again.. it dies again and so on.

I took it home broke the carb down and cleaned it real good and pulled reeds to inspect them, reeds look good carb needed some cleaning, also pulled the tank and took the plug out for a compression test ( yes I made sure the plug wasn't the culprit ).
To my avail, I noticed the plug looks a little beat up and I also think I see copper colored shavings on it and around the intake port.

The compression came back good actually at 175ish but im concerned there's an issue that may involve me doing a teardown?


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Unfortunately at the very least your going to have to pull the cylinder at this point but I suspect you"ll find those shavings are coming from the thrust washers on the big end of the rod which means the crank will most likely have to be replaced. I picked up an R with a blown engine & it had those exact same shavings in it & it was from the crank starting to melt down. Sorry for the bad news.
 

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Discussion Starter #3
pulled the head off last night and things don't look to good. piston is beat to shit, cylinder walls are worn and the head has some pitting although not as bad as I expected, I also suspect its either thrust bearings or if im really lucky a wrist pin bearing coming apart. I will keep tearing into her, she's in pretty original shape and was used in her years. I've had the bike since 2015 and got it cheap (2k) in running condition so I can't complain

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Discussion Starter #4
is adding a stroker crank while in the bottom end worth the extra money

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I have no experience with stroker cranks but a lot of people run them. If I only had 1 R I'd be more inclined to run a stroker crank but since cylinders have to be set up specifically for those cranks I feel like I'd have to do all 3 of my R's to maintain parts interchangability.
 

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You would just have to get a little porting adjustment and run a spacer plate. I had a ESR 310 cylinder changed from stock stroke to +4 mil. I can't tell you if that did anything to add power because the engine ran terrible to begin with. I went with a better builder and he showed me how crappy the porting was from the original builder. So basically after Pete at Hybrid Engineering fixed the porting, compression ratio, and stroked it I had a completely different engine.
I do however think I will add a +4mil crank to my next engine build for the added torque.
Loren
 
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Discussion Starter #7
would a 4 mil fit without modifications to the cases? I'm wayyy more familiar with banshees. I can tell you I got the head off so far and it looks beat I took a few more pics the top of the piston is a mess


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Discussion Starter #10
so I got to taking the rest of the top end apart and there's metal in the exhaust and throughout the jug and cases. crank doesn't seem to have up and down play and feels very free. there's some side to side how much would you say is abnormal? the wrist pin seems okay as well. looks like the piston has A lot of ware (forged piston for sure) and the top ring is stuck i can't get it to move. could the piston be causing shaving by any chance?


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I had an air-cooled KDX200 lunch a piston skirt. I figured for sure that the metal from it had ruined everything. Nope! The rod end and up & down play was fine and the crank was fine too. A mechanic told be to run a power washer with the bike upside down to get the metal out. He said he wasn't surprised at all that everything else was fine. New piston, rings and wristpin plus a hone from him and I was good to go. This "catastrophic event" ended up costing less than $100 in '90s dollars.
 

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Discussion Starter #12
a power washer with the bike upside down? like you sprayed it into the cases?


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You don't need to get the wand that close to the crank. Also spin the tires by hand in gear both directions the entire time to get the crap out. Be aware of gaskets and seals so that you don't ruin them. The crank will take the brunt of the water, no need to "blast out" up close. Then dry with compressed air and hit it with plenty of WD-40 to get the last of the water out. Change the transmission oil afterward then check the new oil for milkshake after a few hours of riding.

The worst that can happen is that you have to split the cases to replace the middle gasket due to an air leak but at least you didn't have to buy a new crank, rod and bearings. Maybe you'll ruin the bearing seals but try to not let that happen by not using the washer as a laser.
 
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