Having diagnosed the reason(thanks Andy)for the siezure-oil pump seal slipping on it's shaft-,I am going to attempt to rebuild the motor myself.I have only ever done basic maintenance to bikes up till now,so this is a bit of a challenge.Anyway,I have sourced the parts and have got as far as removing all ancillaries,and am about to dismantle the motor.I will post photos of the damaged bits for comment,and may need to call for help as I ,hopefully,progress.
Make sure the crankcases are spotlessly clean. It's easy to miss very small dead bits of piston and ring if you don't pull the crank. _________________ Andy.
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There speaks the voice of experience, if there are any bits missing from the rings or lumps of chrome missing from the cylinder then the crank has really got to come out. _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
Got the cylinder off today,the piston has a piece missing from the crown also the hole for the gudgeon pin is smeared .is there a method to extract the pin?
Hello, my engine recently "seized" as well, I think... CAn you explain what happenned when yours went, or did it happen while sitting.
I was out riding, running between 8 and 11 revs, when suddenly I heard a strange noise and had loss of power. I grabbed the clutch and sound went away. After slowing to about 20-30mph, I noticed the engine was not running, so I down shifted and released the clutch. Still had bad noises(kind of a clanking if I remember correctly) so I reengaged the clutch and pulled over. Now the kick lever only goes about half way down, and nothing happens. I have not cracked the cylynders open yet, but wanted some input before I get started. Does anyone have specs on stock diameters, so I can find out how much I need to bore them out, and where I can get a power up kit, (bearings, pistons, and whatever else you think I'll need)
Sorry I didn't mean to jack your thread but it seems like you are a few weeks ahead of me on the same kind of project Bushman! thanks in advance _________________ Mike
You don't simply bore out NSR cylinders. They have to be nikasil plated. Yiou can get a 300cc kit from Tyga for about $1,500. _________________ james
Its not how fast you go...Its how you go fast.
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RC31
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You must find the cause for the event.There are a myriad of reasons for a motor to fail.Post any photos,or descriptions of component condition.Look at the workshop section(engine rebuild).
Admin edit: Make sure the photos are posted in a separate thread. Do not mix the two events to prevent confusion when ideas or solutions are offered.
I am getting desperate,the gudgeon pin will not budge I have tried a puller(threaded bar&pipe),hot rag around the piston,-no joy!!any suggestions?Would a decorators heat gun be appropiate?HELP.
Managed to extract the circlip on one side .I had to resort to using a Dremel to grind some piston away .Got the gudgeon pin out using a puller(threaded bar,washers and a piece of pipe).There is a tiny amount of lateral play at the big end when I wiggle the conrod(holding the little end) what are the limits here?The crank bearings seem fine ,no
movement ,so,am I o.k. to continue with putting the motor back together?
I would have the crank fully checked out or rebuilt first since you don't know its history. _________________ james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm
I wouldn't "have the crank fully checked out or rebuilt first" as it'd cost about as much as decent entire 2nd hand engine and quadruple your build cost. It's very unlikely a crank is going to die and destroy something so just leave it if you value your wallet. If/when it does go you can cross that bridge then.
A replate and new piston or a 2nd hand barrel and piston (and a new oil pump seal) is all that is required here to see you back on the road, I've had this sort of drama before (left the jetting too lean after a summer trackday and popped down to the chip shop) and run the bike again 2 hours later. Andy can half that time. Steve can probably do them at the roadside.
Yes, there is a bit of play at the big end (well there is on mine) and if it's seized it's quite likely that some metal has smeared round the pin, more than a little gentle persuasion is not unusual. _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
I was in Jha's pit when their NSR nipped on about lap 2 of the Suzuka 4hr. They had the thing out there again in about 15 minutes by just sticking a new piston in there and throwing a barrel on. It completed the 4hr with no further trouble.
On the other hand I've seen an NSR spit the dummy in morning warmup, a new top end fitted and run in and then stop again after a couple of laps of the race with a broken big end.
Choice is yours. At the very least give the case a good wash out with some fuel and oil mix. Catch the juice in a clean tray to see if any bits come out. If there's anything nasty then it'll be worth pulling it apart.
Gave the cases a flush,seems clean!Have reassembled the lower cylinder,the siezed one,(haven't disassembled the top one yet),I now hear vacuum and compression. will do the other one tomorrow,work calls
Last edited by bushman on Sat Aug 25, 2007 8:25 am; edited 1 time in total
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