1985 honda 250 sx not starting

[keith0]

hello everyone. I have a 250sx. I purchased it for $150 and its pretty much complete. I would love to ride this thing o some local trails. used them as a kid and have a lot of fond memories. I have also purchased a 200 that runs but stalls and has bad tires so it hasn't gone anywhere yet.

but first the 250sx

so heres the deal. it has spark, its a nice bright blue spark. I have no way of telling if the carb is working. the choke lever is broken by the way.

so to just try and get it to fire up i put a squirt of gas in the head. nothing.
then I tried starter fluid. I pegged the trottle open and hit the starter while i shot a blast of starter fluid in the intake. nothing. tried it again this morning and the same ball of nothing occurred.

I do not have a compression gage that fits the plug hole so I can not check that. with the plug out it feels like there is compression and back pressure but is it enough??? i obviously don't know

so if started fluid will not get it to fire and it sparks very well would that mean the compression is too weak?



******* Just acquired a rubber adaptor that allowed me to check the compression. it very low so that must be the problem.

could there be a stuck compression release? if not. I also have a nice looking piston and cylinder from a 1985 trx250. will it fit?

[coolpool]

Check your valve adjustments. Might be a simple fix or a whole top end job. With tappet covers off, cycle the motor to see if everything moves as it should. On rare occasions your exhaust might be plugged.

[jakep53]

did you have the throttle held wide open while testing the compression??

[keith0]

Looks like it is the cylinder. I looked at the valves and everything seemed to be working fine. so I took the head off and looked at the cylinder and it has a few gouges in it.

I actually have a PC from a 1985 trx 250 but I feel the project is beyond my mechanical skills (and time and patience). I didn't even remember to not any timing marks before I took the cam sprocket off. So thats a problems also.

I did get a lot of good parts for $150. just cant ride them in the mud

[Jmoozy27]

Just rebuilt the top end on my 85 big red. I thought it would be tough but it wasn't that bad. Get a manual for it and do what it tells you. If you have the head off than your half way there. Start a new thread for it and these guys will help you. It a good experience. It was my first rebuild. I just took my time, followed the manual, put it together and it fired right up first crank like brand new.

[keith0]

I just might. thanks for the advice

[DohcBikes]

Keep it in this thread.

One thing I'll say is not many here have the stones to admit they don't know enough to build an engine. Lots of trike engines in pieces out there... Lots of engine build threads that never go anywhere, so think about that. Some wanna ride so bad that they decide they are also a mechanic. Unfortunately not everyone is.

Let me know if you need any help including machine work. Unlike many here that have done one or 2 top ends, in their life, I rebuilt 3 Honda motors just this week. And one Kawasaki. Just be glad it's not a Vulcan 1500 with a bad crank

Get a Honda service manual and keep that humility on tap, you may be one of the few here that finishes an engine build.

[blowre1]

A top end job is not bad. I had an engine rebuild that went south also, so DohcBikes is telling the truth. Buy a paper copy service manual on eBay. They aren't the best, but it's better than you left to your own devices. The timing is not a big deal to sort out. The tech manual/service manual has that, or it may be in the forum. Or I could tell you here.

If you have fuel, spark, and compression your bike pretty much has to start. I wouldn't put fuel in the cylinder, though. My dad taught me the following trick to start gass engines with fuel problems and it has never failed...
- pour a little clean gasoline into the top of a spray can or cut-off bottle. If you have electric start, push button and turn over engine as you dribble gas into the air filter while working throttle linkage. Go easy on the gasoline at first; just a tiny bit, then add a little more as needed. I prefer this to starting fluid. Your engine will kill when you stop pouring or it runs out of fuel.

G&H ATV has a top end service on ebay and their website for Big Reds/250sx. Call or email for details about that.

I would advise against going past the left or right covers on your rebuild. I did it once and was okay. Had to a second time and f-ed up the transmission among other things.

Good luck