1984 250r wont stay running

[seth6025]

So its been awhile since I was last on. Bike was running fine then died like it ran out of fuel. Now it will start first or second kick but only idles for a few seconds and dies also if I try to give it fuel same thing. So here is my list of what I have checked.
New Plug
Boots for cracks
Reeds---checked and cleaned
Carb---been off several times and run through ultrasonic cleaner with jets passage ways all blown out with air. Everything is clean
Fuel Filter---Replaced inside tank filter
Petcock---New
Fuel Lines---New
Tank Vent---Working
Flooded base---No
Electrical connections-----Pulled and cleaned with contact cleaner.

So im left with CDI, Stator, and Coil.

Any ideas cause im running out and I cant seem to find a cdi online for this bike.

[Footy]

Is there any chance there could be an insect nest (like dirt dobbers) inside of the exhaust. This has happen to me once.

[seth6025]

Is there any chance there could be an insect nest (like dirt dobbers) inside of the exhaust. This has happen to me once.

Don;t think so as its been stored inside my garage the whole time and good amount of exhaust is coming out but I will take a look just in case.

[whiteman350x]

Test compression. I have had a couple that would fire up but not have enough compression to keep running.

[seth6025]

Test compression. I have had a couple that would fire up but not have enough compression to keep running.

Oh really, I figured since it started so easy compression must be good. I will check that tonight I guess. Thanks

[seth6025]

Ok so I have checked exhaust and nothing blocking it. Also did a compression test and showing 170psi. Any other ideas? Im really not sure what else to try

[seth6025]

could a bad stator cause it to start and die? even giving it fuel I cant keep it running

[sjsst41]

Crank seals? I’ve heard of spraying starting fluid with the stator cover off at startup and see if you have an idle change (at least you can test one side). Kind of a long shot, but it’s something to check.

[ATC King]

You're most likely missing something simple.

Also, NEW means Never Even Worked. It's one of the most infuriating outcomes when trying to repair something and the very part that was new turns out to be the problem. That includes spark plugs.


Sure, the CDI could be the problem but without having a known good one in hand to swap out, that can be a rather expensive guess. Electronics age just like anything else, especially the capacitors in a CDI.


Is the enricher on the carb messed up somehow and just smothering it with fuel?

Have you dissembled the on/off switch to have a look? If something is loose in there, as soon as it starts, the vibrations could be bouncing the contact around and shutting it off. Those switches are seldom dissembled and can get pretty nasty. They're not sealed from the elements in any way and it's not uncommon to find spider webs in them. I make it a habit to clean those every 40 years or so, you can't be too proactive with switch maintenance.

[seth6025]

You're most likely missing something simple.

Also, NEW means Never Even Worked. It's one of the most infuriating outcomes when trying to repair something and the very part that was new turns out to be the problem. That includes spark plugs.


Sure, the CDI could be the problem but without having a known good one in hand to swap out, that can be a rather expensive guess. Electronics age just like anything else, especially the capacitors in a CDI.


Is the enricher on the carb messed up somehow and just smothering it with fuel?

Have you dissembled the on/off switch to have a look? If something is loose in there, as soon as it starts, the vibrations could be bouncing the contact around and shutting it off. Those switches are seldom dissembled and can get pretty nasty. They're not sealed from the elements in any way and it's not uncommon to find spider webs in them. I make it a habit to clean those every 40 years or so, you can't be too proactive with switch maintenance.

Good point...I will try another plug and recheck the carb again. Never thought about kill switch but I will check that as well. Thanks for the input. As for CDI does anyone have a lead on where to get one? All I can find is used ones on ebay for over 100 bucks plus shipping. Would rather buy new if I need one. Mine is the 2 connector not the round one. Also the pins inside are horizontal and most I find online seem to be vertical.

[ATC King]

You're welcome.


I learned the hard way to check connections and electronics for issues with vibration and since then it's just something I go straight to if the symptoms point anywhere to it being a possibility.

I had an old bike that I was already tired of working on because parts were hard to get and expensive, and the machine wasn't worth much. That was back in the days of dial-up and chats rooms. It would start and run alright, but under load, at certain engine speeds, it'd start to miss really bad. Already being fed up with the whole experience and just wanting to be rid of it, I sold it.

It turned out to be a wiring issue and a simple fix. I didn't take a big loss on that bike, but I felt really defeated when I was told what the issue was. That one left a scar because I knew better and should have been more thorough.



Which brings up wiggle testing, and that is an actual term. Wire harnesses can look OK on the outside and still have bare and broken wires on the inside. On older bikes and ATVs a common problem area is where the harness goes to the handlebars.

A simple test, while not completely accurate, would be to turn the bars one way then the other while starting. It'll be evident if there's a wiring problem.

A proper wiggle test would disconnecting harness ends, supplying power at one end and connecting at light at the other, then wiggling the harness to see if the light flashes. That's a simplification, wire gauge and current need to be accounted for to prevent damage, but you should get the idea and can research that method more.

Here's a short article about wire issues on aircraft: https://lectromec.com/the-scope-of-chafing-on-aircraft-wire-and-its-impact-on-wire-reliability/

Even engineers have to devote a good amount of time and effort in preventing those types of issues. If it's got lengths of wire, there's potential for failure, even with relatively short run time. I think the early F-14 had some serious wire chaffing issues and while looking for an article about that, I seen that some Ford F-150s had recalls because of wire chaffing.

I don't even want to think about something like an aircraft carrier, especially if it took battle damage. I would think those have built-in redundancy out the wazoo, or independent modular systems.

[seth6025]

Awesome, I will try moving the bars around as well as all the wiring. Your right you never know

[seth6025]

Ok so more info. I got the bike running but only at idle. Give it any gas and it shuts off. Now one of the times I had my head by the motor and gave it a little gas. It stumbled backfired and shut off. But I’m almost positive I seen white smoke shoot out from between the fins by head gasket. Now would this make any sense? Would leaking head gasket cause the issues I’m having? Also it held a compression test at 170 for awhile and did not leak down so can the gasket be leaking but still hold compression some how?

[El Camexican]

I’m suspicious of your base gasket. It has no effect whatsoever on compression and it’s difficult to get the engine to rev up if it’s leaking. It can also cause backfiring. The proper way to test for a base gasket, leak, or any other leak on a two stroke engine is to do a pressure test.

[BOB MARLIN]

I've seen a few fly wheel "rivets" come loose ( including mine) where the fly wheel is connected to hub, causing the all kinds of problems with timing. I've also had carbs that leaked around the jets and adjustment screws because of cross threading or just plain worn out, making it impossible to get the mixture right. Cracked spark plug wire shorting out to the frame at higher rpm is another.

[seth6025]

I’m suspicious of your base gasket. It has no effect whatsoever on compression and it’s difficult to get the engine to rev up if it’s leaking. It can also cause backfiring. The proper way to test for a base gasket, leak, or any other leak on a two stroke engine is to do a pressure test.

Another person mentioned this to me too. I dont have a leakdown tester but I think I may need to purchase one

[seth6025]

I've seen a few fly wheel "rivets" come loose ( including mine) where the fly wheel is connected to hub, causing the all kinds of problems with timing. I've also had carbs that leaked around the jets and adjustment screws because of cross threading or just plain worn out, making it impossible to get the mixture right. Cracked spark plug wire shorting out to the frame at higher rpm is another.

Ok good to know. I will take a look at that as well

[Fox250R]

I know you said you cleaned the carb but did you blow out your pilot jet?

[seth6025]

I know you said you cleaned the carb but did you blow out your pilot jet?

Yes cleaned twice. Second time ran everything through ultrasonic cleaner and then blew compressed air through everything and reassembled