This Trailfire is getting to me

mwking · Post by **mwking** » Sun Feb 22, 2009 1:11 am

If you have missed my previous posts my '82 Trailfire has melted two pto pistons this year. It was completely rebuilt over the summer. After it melted the first piston I redid the engine again with new gaskets and seals (again) only to have it melt down another piston a couple of weeks ago. After the second time I went through the carb and double checked the jetting, when I compared the main jet to another one I could see that the hole in it was smaller than it should be due to some corrosion. I got a new jet and put it in along with another piston figuring I had found the culprit.

I noticed when I got it going again that I had to turn the idle speed screw in almost all the way to get it to idle at 2000 rpm. We finally got some more snow so I took it for a spin last night. It ran pretty good although it was bogging when I started out, but it seemed a little better at the end of the 15 miles I put on it. Today I took the carb off to give it a good cleaning figuring that would solve the idle problem. When I put it back on it seemed even worse, the idle speed screw is all the way in now. I took it down the road and it was bogging more, when I got back to the house I stopped and could hardly keep it running with the throttle wide open. After it cooled down it started back up and would rev up again. I wondered if my two month old coil was failing so I swapped it for another one. I checked the plugs, they were black and oily, I cleaned them up and put them back in. I took it out for another spin and after a short run I stopped and it would not rev up, but after pulling it back home I was able to start it and drive to the garage.

I didn't have this issue before the latest repair and I don't know what could be causing it. The only other thing that I have done is add a tether kill switch. I tried unplugging it just to be on the safe side and there was no change.

Murray

oscar89 · Post by **oscar89** » Sun Feb 22, 2009 2:45 am

Too heavy on the oil injection?

big danno 1970 · Post by **big danno 1970** » Sun Feb 22, 2009 3:05 am

Murray,sounds like the choke is hanging up for some reason or maybe the rubber on the plunger is hard and not sealing.If you would like I could come over and have a look.Sometimes just an extra set of eyes/ears can help.
Dan

mwking · Post by **mwking** » Sun Feb 22, 2009 1:36 pm

The oil injection on this machine is long gone. It was removed when I got it. Because of the new piston I am running it about 30:1 for the first tank, I know it's a lot of oil, but it has run fine before with this much before and better safe than sorry. The carb is set to stock with the exception of the e-clip on the needle, it is in the fourth groove instead of the third. That would make it a little richer, It was in this groove when I got it, I thought about changing it back, but after melting two pistons because it was lean, it makes me nervous.
I am wondering if it is flooding out somehow after it runs so long and clearing after sitting a while. I don't think it is ignition, but I can swap the CDI to check. I am going to check the fuel pump for a diaphram leak, I replaced it but the Winderosa ones aren't known for quality.

Big Danno, I would really appreciate another set of eyes and ears on this one. I am going to be around and working on this today and tomorrow, I will give you a call.

Murray

427cobra · Post by **427cobra** » Sun Feb 22, 2009 11:08 pm

Let us know what you find out.

Sounds like it is having similar issues that a buddies sled had at the HOF ride this weekend! We leaned out the carbs by lowering the needle, swaped fuel pumps, and swaped coils with no change. He was having the same problem with his 80 LF. Just like yours....after it cooled down it would run fine!

Fun stuff....

400brian · Post by **400brian** » Mon Feb 23, 2009 3:11 am

It seemed like a bunch of the LFs on the vintage challenge were having the same issue.

mwking · Post by **mwking** » Tue Feb 24, 2009 1:14 am

Well Big Danno came over this afternoon and brought the carb off of his Trailfire to see if we could narrow down the culprit. I checked my rebuilt fuel pump and the float needle in my carb and both were ok. We had thought that the carb or the fuel pump could be flooding the engine out. Dan was quick to notice the pto cylinder was knocking when we fired it up. It really helps to have some one look at the sled to pick up on the things you are overlooking. When the head came off it was really surprising how much the piston was rattling around in there. It was definately time to try another piston. We tried the other carb and really didn't notice the difference in the way it idled we were hoping for. I ended up swapping the cdi box and still didn't notice any change in the idle. Finally I dug out another set of new plugs I remembered I had in the Spitfire and put them in. When it fired up it was idleing higher right away and I had to back the idle speed screw out as it warmed up. I took it out for a run and it seems to be running fine now. It's nice to make it back to the house without having to call for a ride.

Murray

427cobra · Post by **427cobra** » Tue Feb 24, 2009 12:29 pm

So you think it ended up being the piston and plugs? Did you do a compression test as well?

big danno 1970 · Post by **big danno 1970** » Tue Feb 24, 2009 6:05 pm

Actually we changed the cylinder as well.I think we may have been able to go the next piston size up it was that sloppy.I suspect the original plug we put back in was the cause of the idle problem after the cyl/piston swap,changed plugs and presto magic she idled.

JDT · Post by **JDT** » Tue Feb 24, 2009 8:07 pm

Is it possible that there was a STD piston is a 20 over jug?

Found one like that last you.

River Rat · Post by **River Rat** » Tue Feb 24, 2009 8:31 pm

Murray..Just a little tidbit of info.. Sometimes to much is way to much.. 30-1 is alot..Too much oil creates heat and we all know what to much heat does..

Frankie

mwking · Post by **mwking** » Tue Feb 24, 2009 8:51 pm

I don't have a dial bore gauge, when I measure the top and bottom of the bore they are in spec, but that is the least worn area. I suspect that a dial bore gauge would find the cylinder worn larger that it should be in the middle. So it's not a .020 over but it should be. The piston that was in there is worn somewhat compared to a new one too.

River Rat: I don't usually run 30:1, only after I have done some engine work. I have been running 40:1 normally though.

Murray

big danno 1970 · Post by **big danno 1970** » Tue Feb 24, 2009 9:26 pm

River Rat wrote:Murray..Just a little tidbit of info.. Sometimes to much is way to much.. 30-1 is alot..Too much oil creates heat and we all know what to much heat does.. Frankie

Actually the oil does not creat heat per say but what it does do is displaces gas and that could cause a lean mixture but I dont think 30:1 would cause that much trouble.Alot of the old sleds used to run 20:1 and when or if you switched to 50:1 then they could run rich.
Now all that being said most if not all manufactures jetted the sleds for -20 or -30 degrees celceus (dont know the ferinhieght conversion or how to spell ferinhieght) so even if you ran 20:1 I dont think there would be much of a problem except maybe the odd fouled plug.