350x Saga

[patriot1]

1985 350X ran and rode good. started easily. It had an exhaust bolt broken and another one missing. I pull the engine and took it to a machine shop to be drilled out.

Machine shop guy told me that I had to pull the head, so I did and took just the head back to him.

By the time he got it drilled out and ready, I had let the cylinder get surface rust in it. I ordered a hone. I honed it and it cleaned up nice.

I put it all back together and put it in the bike and it wouldn't start and run EXCEPT when I sprayed starting fluid in it.

I checked timing and valves over and over.

I checked compression with HF tester that had never worked and had 30 psi...I bought another tester from auto zone and got 60 psi.

I watched MRC's videos again and again.

I figured that it would not start on starter fluid at 60 psi and I figured it was the carburetor. I actually had a 223 cycles Curtie built 350X carb laying around.

I removed the carb and realized it was off of a 88 250X...(Hmmm interesting)

I put the Curtie carb on and nothing. Not even a pop.

I bought fresh gas and nothing.

Curtie carb popped with starting fluid.

Now I am back to thinking compression...maybe I rolled a ring?

Would a low compression bike run on starting fluid and not high octane gas?

Thoughts? advice? Prayers?

[Jim mac]

did you go back and check to make sure you didn't install the cam chain off by a tooth?jim

[patriot1]

I called myself doing that Jim

As well as checking the valves

As well as loosening the drain screw and making sure I had fuel flow.

Then I had a thought...WEAK SPARK!!

I went out today and checked for spark. I saw spark and then I didn't or maybe I did because it is had to tell when you are kicking it....

So I recorded with my phone and saw spark but not all the time.

I went to get my 82 year old neighbor to watch for spark. He is a real mechanic, unlike myself.

A few kicks later he confirmed...WEAK SPARK.

I changed the plug and big blue arcing sparks!!! YEE HAW

I put the 250X carb back on it and then went and put my boot on and kicked it about 45 times...

ABSOLUTLY NOTHING...Not even a hint of a pop.

Sprayed some ether in it and it started on the second kick and ran for less than 9 seconds

Tried to start it with out ether and nothing.

I came in for the night

[Jim mac]

I had a intermitten spark issue last year on a new to me 200x. it had weak spark with the plug in it, no spark with a new plug, changed the coil cdi harness since I had extra stuff. finally swapped the stator and it runs fine.
I'd go back and try another compression test. kick it a good 10 or 12 times. jim

[patriot1]

That's the next plan.

Thanks Jim

[350for350]

Be sure to hold the throttle wide open while you're doing the compression check. Did you get your decomp problem figured out?

[patriot1]

Yes 350! Or maybe I will remove it all together.

I did get a new cable. Installled it and it kicks much better. I still need to adjust it and I don't understand what "1/14 of an inch freeplay" that is in the manual means. But I will get to that later.

[knappyfeet]

Thoughts? advice? Prayers?

Prayers.

God I hate when this happens because it happens to all of us at some time and it's frustrating.

I would assume that if it ran and started fine before you pulled off the head and honed the cylinder.......and with all things being equal it won't now....that it must be something with the head or cylinder, etc. Unless of course other problems just started to manifest at the same time.

I'm curious....when it ran for about 9 seconds...what did it sound like? Any abnormal sounds? Any abnormal running issues in that 9 seconds?

Because to be honest it sounds like a spark or fuel issue. A fuel issue especially if it ran fine for those 9 seconds.

Good luck.

[ATC200X4716]

Did you put new rings in the honed cylinder or use the same rings? The rings lap in to the cylinder, so a re-hone needs new rings. You may have a worse ring seal than you did previously. Any chance of having someone tow you to pop start it? I know that is no easy task on a 3wheeler sometimes, not to mention on a 350x, but the extra speed may build you some compression to get it to fire. Yes ether is more volatile and will ignite at a lower compression than gasoline so it kind of makes sense it fires on ether and not on gas if the compression is low. Of course make sure can timing is correct and valves have some clearance.

[MrConcdid]

Hey Patriot1,

Man I hate this for you. I pulled my 350x engine 3 times, before getting it right, never the same issue. did you install new rings? did you put the piston in backwards? did you check the ring gap in the cylinder after the hone?
Literally mine popped once and only once on starter fluid the time I found the collapsed rings. Now that you know you have good spark, and I'm sure you checked the timing 100 times (me too) I would feel confidant is saying pull the engine 1 more time, verify the answers to the questions above. who knows you may discover something else during the tear down. I am betting collapsed rings.

I wish I was closer to help.
MrC.

[ps2fixer]

It's hard to say for sure what's going on, but if you're confident rings, valves, etc are good and the compression loss is likely from the hone job (even a freshly rebuilt engine can be low on compression at first till the rings seat), I'd try to run it on propane. Portable propane torch stuffed in the carb with it full blast open (don't light it) and kick it a few times. It should bare min pop on it, generally it can run small engines at idle pretty well and should be enough to solve fuel issues for short term testing. Run it for a bit to let it warm up a little and have the rings seat some and see if you can remove the torch. If you remove it and it dies, I'd say there's also a fuel related issue, plugged jet, that type of thing. If it stays running, I'd run it easily and give it a good heat cycle, let it cool off and see if the compression jumped up much.

General rule of thumb is an engine will run on 100 psi of compression, some lawn mower engines spec around 80-90psi, so 60psi might be on the low end of what's possible to make a gas engine run. The actual stock compression is much much greater though and is far out of spec, going off memory but pretty sure it's 150+ psi for the spec, might be like 170ish been a while since I looked, the higher spec is mainly from the higher compression engine.

Of course if you're nervous around propane, don't follow my advice, there's a possible chance a back fire could ignite the torch so be mindful of back fires. I've never had one light, but it's been a great diag tool since the torch mixes the fuel quite well to run on for short term tests.


For spark issues, get a spark tester that physically has a gap, the PET-4000 is a good one, most typical engines you test them at a 6mm gap (1/4 in), if it can't make that jump, it has weak spark still. Bright white/blue spark does not guarantee good spark, but yellow/orange spark does guarantee weak spark (even though sometimes it can run on it still). Automotive coils can jump like an inch, but they operate at a higher voltage.

[patriot1]

Wow! Thanks guys!! I will follow all advice before I pull the engine again.

Here's an update.

I ordered a compression tester like the one shortline suggested. "Buy once, cry once" MrC

I had 100 PSI, nothing more with oil in the cylinder.

I ordered a leak down tester (per el Camexican)

It was $30 and junk from amazon and it didn't work right.

It got cold and wet for a couple of weeks

I decided to use the China leak down tester today and....


Air freely flowing from the exhaust, so that's good, I was expecting from the dip stick hole.

I'll look at it again soon and update y'all.

Thanks again!!

[patriot1]

So, after I slept on the air flowing freely from the exhaust, I realized that when I put the air in it, I had knocked it off TDC.

Glad I realized that.

Went back a few days later and made it to where the engine wouldn't spin when I put air in and tried it again.

Cheap, China, Amazon leak down tester leaked air from and around the gauges so I quit for the day and returned that one.

Ordered another one, I think it was OTC brand and when it arrived improved quality was apparent.

Used it today and ran it up to 50psi. I was not comfortable putting 100psi in the bike.

Engine was losing 40% of air with the majority coming from the oil stick hole.

Like I thought, I need rings, like ATC200X4976 also said.

So now the engine is coming back out.

Much better knowing what is wrong after properly diagnosing.

I do think that I could have pulled it and got it started and maybe it would have built some compression

Anyway: Here is a picture of the culprit

[MrConcdid]

Lord of the Rings. My pretty.

[patriot1]

Back at it finally.

Engine out and torn down, look at pics and then tell me what you see?

Where did I screw up?



Look at the up and down vertical marks?? Normal?



Is the bottom "oil ring" Supposed to be proud?



top of piston



valves

Thoughts? Prayers? Advice?