I sold the sportsman efi machine that I had so I am looking to get back into the more nerve friendly older machines. I am going to go look at an early 2000's trailblazer 250 that has some running issues. The guy said he had a fresh top end put in it but put about 25 miles in it when it started to die and not want to run. He says it will run if it is fully choked but has a low idle and will die if throttle is applied. He thinks the oil injection wasn't working and he took the cylinder out again. I am having a hard time believing the oil injection failed because I thought the 250's were pretty bulletproof in that area. I am more leaning towards a few other issues-

1. A carb related issue. Maybe a plugged jet or other issues that could be resolved with a carb rebuild.

2. Bad crank seals. Leaking seals causing a poor mixture if they weren't done at the time of the top end being done.

3. A bad carb boot, which seems to be a common problem on these.

When I go to look at it, I plan on bringing my bore scope to look down into the cylinder and also my compression tester to try to eliminate a bad too end. What else should I be looking for? This is a really clean machine and has brand new tires all around and I can pick it up for what he put in it for tires so it would be a nice little project for the kids to buzz around with.

Thanks,
Mike

 

Sounds like you have it pretty well covered.Oil pumps on the old 250s were reliable,but if he didn't bleed the pump(if he remove the oil lines) or premix the first tank of fuel,piston and ring wear can start immediately and crap out a little later on even if the oil pump catches up. By the sound of it dying on him that could be the reason or the carb has trash it,gets stopped up or a crank seal leaking enough that you'd have to have the choke on to help compensate.Another could be the reverse limiter module failing.They can retard spark and act the same way in forward range.Just pull the black wire on that.

 

Could be just clogged jets as well...choke on to run/idle is indication of clogged idle circuit (pilot jet).


Simple solution to oil pump is to disable & run pre-mix...I know it's a hassle, but it eliminates the "possibility of it failing on you before you catch it and blow a motor syndrome"...

 

People still lump together the 400 oil pump failures with the dependable 250 and 300 oil pumps. The 400 had the problem of being directly exposed to mud and water. Pumps would freeze up/corrode and couldn't deliver enough oil to lubricate properly. I don't know how many people have brought in 250 and 300s to the shop when they quit running and seized and blamed the oil pumps. Problem was the owners went too far between having top ends replaced.I've found so many pistons that when you put a micrometer to the base of the cylinder and base of the piston,many would come up showing .008,.009 or even more.Way past the .005 max allowed. Plus many kept riding them when they sounded like marbles in a tin can from piston slap.This I showed to the owners,then repaired their machines,premixed the first tank 50:1 to help in break in. The final step was to lift the pump arm up fully to trick it into pumping wide open and you could see the oil go from the pump to the cylinder base on the 250 or the carb on the 300.Then sent them on their way and never had a comeback on these.To this day people are still scared of all oil pumps because of the problems on the 400.

 

Thanks guys,

I'm leaning towards some trash plugging the jet on the carb causing it to run poorly but I guess I completely forgot about the reverse limiter. I was going to check the ETC when I looked at it but just figured if it was an electrical issue it would probably not run at all. The oil injection system is something I will definitely keep, especially if they are durable like OPT says. I don't like to mix fuel and it is a pretty good set up they have so if it works, I will leave well enough alone, lol.

Thanks,
Mike

 

Thing is that a faulty limiter could mimic a carb problem also. Some would crank up and idle ok,some were hard starting,others would die when you placed them in reverse and others would limit in forward. If I had my way I'd defeat every limiter I could find by pulling its black wire. Not having to push the over ride to have full power in reverse is nice.Most other brands didn't even have reverse limiters. Just a crappy safety device that didn't last.If you do this make sure the kids know it will have full power in reverse before they ever get on it.

 

So...first off...my post had nothing to do with being "still scared of all oil pumps because of the problems on the 400"...


I've had/have several 400's and never had an injection issue...


Fact is...they DO FAIL (and do so without the operator knowing it's happening). And if it fails 20 miles out in nowheresville...then...well...you get the picture...

 

ive recently went thru top end swap on a350 2stroke 91 . i had two moters , and wanted to use both, and spend little money. The bike had broke piston. With advice from old polaris tech, i did compresion check to locate this issue. 60 psi. Me being cheap i used gasket maker. mistake ran realwell short intervels. heat broke down for gasket lost compression. with that said the guy told u he went into top half, may b he was cheap like me. Gasket kit 18.00 bucks

 

You wont know what someone else has done unless you have to back track on the work they say they've done. Had plenty of machines come into the shop that owners said they installed a new top end only to find that they stuck a new standard piston in a worn cylinder bore. Most times it costs less in the long run to do a job right rather than skimp on parts,gaskets,etc as you've found out. Hope you get it up and running right.

 

Well I went and bought the little machine. Pretty solid and tight so I think I did alright with the price. Haven't had time to do much to it since im finishing up a 350 two stroke for a friend and have to run to the machine shop to finish the cylinder. The little 250 does have compression by just feeling it by pulling the recoil and the oil injection did have oil dribbling out of the line when I pulled it off the carb. I will do a compression test and see where I stand and check out the couple things OPT recommended and hopefully I will have a nice little machine for the daughters.

Thanks,
Mike