1985 honda 350x cant start/ black plug

[Jackrwesty]

I went to buy a 350x the today but they couldnt get it started so I didnt buy today.. they said they had it running last weekend and was ripping up and down street. I do believe that . It's a pretty clean original trike. But they were kicking and kicking and no luck! They said it is usually tough to start, even for a 350x. The plug was black when they took it out...what would cause that??

Also, they took the oem carb out for some aftermarket one, I will swap that right out if I buy it I think that could be a problem .

Is there any other reasons why it would start? According to them and let's just assume it runs good. Valves be an issue? Thanks!!

[MrConcdid]

black wet gas dripping plug = way to rich carb outta adjustment
black dry carbon covered plug = running kinda rich with a weak ignition system could be bad plug.

That's great that it wont start! you should be able to buy it alot cheaper. if it looks good get it, then fix it.
MrC.

[Jackrwesty]

Thanks I'll start going thru it, just picked it up!

[ATC King]

Weak ignition? Low compression?

The carburetor isn't the only thing that affects how they run, and it's not always an 'easy' or 'cheap' fix like suggested in so many sales ads.

It takes all of a few minutes to check compression, for real, with a real compression gauge, not just sitting an obese squirrel on the kick starter to see if it moves. Didn't move, passed compression test. Squeak, squeak.

You can find free manuals online. Definitely go through the specs, check things, then go from there. It'll save some time and give you some idea of overall engine condition.

[350for350]

This wouldn't cause the black plug, but yes, do check your valve clearances. Mine is a lot easier to start after I adjusted the valves. Use a feeler gauge too. My "close enough" wasn't really close the first time.

[ATC King]

A tight intake valve can make one act like it's running lean though. It'll cough, and be hard to start. If it does start, it typically wont idle well or take throttle.

[Scootertrash]

not just sitting an obese squirrel on the kick starter to see if it moves. Didn't move, passed compression test. Squeak, squeak.

sAY WuT??!??

Get rid of that aftermarket carb, hopefully you got the original carb when you bought the wheeler?

I don't care what anybody here says, aftermarket carbs are a crapshoot and mostly Chinese junk.

I've salvaged, cleaned, and rebuilt some pretty nasty factory carbs. You can also buy new carbs made by the OEM manufactures that will fit and work just like the original.

[ATC King]

sAY WuT??!??

Ha! Just playing about the people who pull the rope or move the kickstarter and they 'know' the compression is good. While people who are very experienced with a certain engine and have owned or worked on many get the feel for it, there's a lot of Joe Blow sellers out there fishing for suckers. Compression numbers are easy to get, and several auto parts stores loan testers for free. No reason to not have proof unless it's one of those sellers. Selling a non runner with good and tested compression would actually help sell it.

I don't care what anybody here says, aftermarket carbs are a crapshoot and mostly Chinese junk.

Trying to sort something out with a non factory carb is definitely adding another unknown. Even if the Chinese carb itself is good, the jetting may still be off. Starting off with a non running trike and adding a Chinese carb to the mix isn't moving in the right direction, for sure.

[ATC King]

I found ignition spark specifications while looking through my Yamaha manual. I don't know if Honda list anything like this for the 350X. Maybe someone with a good running 350 will go through the trouble of recording a baseline? It sure would help the community.

These pictures show using the Yamaha branded electrotester, but I'll mention another option after these manual images.
Attachment 264019
Attachment 264020
Attachment 264021
Attachment 264022

It looks like the spark gap function on the Yamaha tester is just a manual device, which increase the gap seen in the window.

In that case, a inexpensive tool like this...https://www.walmart.com/ip/Mgaxyff-I...e8a09cd35c3a17


...will do the same thing. This is designed to be used with the engine running, but it'll work either way and is hella easier than trying ground the plug where it can be seen while kicking.

I personally like this tool...https://www.ebay.com/itm/Snap-On-MT2...0AAOSwNmpfGnfA
Attachment 264023

I like this one because it's noninvasive. You don't disturb anything since it uses and inductive pickup. The reading isn't a gap but in KV energy (approximate). You just scroll the wheel while the engine is running and what the light go from solid, to flashing, to off. Somewhere where it goes from solid to flashing is the spark energy. There's plenty of old ignition tools available for cheap that will work on trikes, just the same as anything with a spark ignition. Probably some old boat CDI testers that'll work and are cheap.

I'm wanting to point out that spark can and should be measured if there are engine performance problems, not just if it does or doesn't have spark. It's much easier for a new plug to fire outside of the engine than it is for it to do the same with compression and fuel, that's why measuring the spark is important. The higher the compression, the more energy needed for good combustion (Paschen's Law https://en.wikipedia.org/wiki/Paschen%27s_law)

You've got to have a good baseline though, if there aren't specifications listed by the manufacturer, like Yamaha put in their manual. A lot of people waste time chasing carb issues when it's actually ignition.

[Outdoorgirl]

Check the air filter?


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