A forum for owners of Yamaha TTR250 trail and enduro bikes!

Wow - never ever seen a TTR conrod bent like that!!  

The engine must have come to a very sudden halt so it's worth doing a very thorough check as I am sure you are doing!

A hydraulic lock may explain it if the bore isn't damaged. What' are the head and valves like? 

Another first for me is your engine number. I have only ever seen engine numbers prefixed 4GY for the white TTRs and 4PX for the later blue models with the plastic tank - approx. 2000 onwards. Does anyone else have a blue TTR with an engine prefix other than 4PX?

I wouldn't worry about ordering the wrong parts as there has been very little change in the engines since they were introduced in the early 90s up until production ceased about 10 years ago.

I am interested as to what your plans are for the rebuild. Assuming no other damage to the engine and gearbox, are you going to get the crankshaft rebuilt with a new conrod kit or look for a second-hand one in good condition?

Brian

Thanks for the quick responses!

- Good to know the engines didn't change much over all the model years so not to worry about parts - thank you

Bought the bike as a project - previous owner got it on a trade and had it for 8 years in his garage with intentions to repair. Some parts were lost before I got it, so will have to source out things like a throttle assy, oil line banjo bolt, rear brake pivot bolt.

- A Crankshaft repair machine shop in a nearby town will replace the con rod for about $250 cdn including parts
- the bore looks ok, some minor surface rust (i hope) no noticeable ring ridge
- head and valves appear ok but will check them furthur
- oil was clean, but as mentioned the previous owner may have put in fresh oil after the incident
- will know more once I get the cases split this week but the Rebuild plans so far are:
connecting rod
crank bearings
piston/rings
hone cyllinder
cam chain while i'm in there
all gaskets

There is excellent info on this site - thanks to everyone who contributed up to this point to help fellow riders like myself! Looking forward to getting out on this bike (never rode a TTR before!)

Pleased to hear the forum has helped and that you have had good parts support from Steve 

I have to say that your workbench has got to be the tidiest and best organised that I have seen - marvellous 

Update: Got the rebuilt crank back on Friday, the engine is all back together and now runs! Using a solenoid jumper button for cars, I cranked it over for 10 seconds or so for a few times with the ignition off to build up oil pressure before starting. Used the oil pressure check bolt to ensure oil was flowing. Started up easily, idles fine and revs without bogging when I 'blip' the throttle. (carb was rebuilt too)


What do the pros on this site do for engine break in after a rebuild? For my YZ 250 rebuild, I did a few heat cycles and rode it easy the first couple of times. I will do the same to the TTR unless there are other recommendations.

How soon should I change the oil after the rebuild? Won't be riding for a bit, there's still a couple feet of snow on the ground and it's -14C here at the moment.
Great to hear it finally run - Thanks to the great members on this site!

Looking good on those tyres! Congratulations on the rebuild.
Oil disappears from the sight glass when running - that's perfectly normal. It's being pumped and splashed round the cases. As long as the level is right when the engine's off it's all good.