Can't Take It Off Choke

Michael Cardamone

XS400 New Member
Reaction score
So... This kinda feels like AA, "Hi My name is Mike and I have a problem." JK. But in all seriousness, I'm hoping a few kindhearted Journeymen XS-folk can lend me some knowledge.

Experience level: Noob, like total, complete noob...
Bike: 1981 Yamaha XS400HS
BLUF: basically, bought diamond in the really rough and wish to get it working... Again

Background: Had it sit for some time during my moves across the Northeast (covered at all times with preservative in the fuel. I'm no dummy!), had my friend ride it when I bought it and rode it for about 30-40 miles until it decided to quit in downtown Rhode Island last summer (but was having a blast beforehand!). At the time I managed to choke it all the way out and limp back home. That was this past summer, now fast forward to now (November of 2023) and I've got the sudden inspiration after another move to get it working.

Problem 1: I kick start it to life with the choke all the way out. let it run for about 30 secs and then push in the choke halfway, anndddd it stalled... it does this every time without fail. Now I'm assuming you start it this way, I was given a crash course by the previous owner so it's basically his word that I am abiding by.

Problem 2: I hit the electrical starter, and it goes "click click click click" like its shorting out somewhere. The wiring harness looks right f***ed so I'm assuming it a poor connection or a broken wire somewhere (I suspect it's around the steering column because when I turn from left to right a few times while holding the starter button it can sometimes work)

Problem 3: Exhaust leak at the outlet of the cylinder, I tightened up everything farm boy tight since I don't have a rachet set nimble enough to get behind the frame. that seems to have been sorted as of tonight after letting things heat up and expand/ fit together but will probably return in due time.

Problem 4: While I was removing and refitting my exhaust on both sides, I noticed there was a ton of carbon build up in the cylinder, and before you say "uh yea no duh it's an engine" answer me this: is there an acceptable threshold for carbon build up in a cylinder? And what is that upper limit before it starts hindering the effectiveness of that cylinder? If that is even a thing?

Problem 5: The carburetor boot has some kind of surface crack in it along its side. I sprayed starting fluid on it while it was running and there was no change in idle, so I don't think it has sprung an air leak yet. just something to keep an eye on.

Thanks for reading Ladies and gents! I'll keep updating as things progress!
Welcome! Let's see about those issues without writing a book.
1. Start it how you need to start it. With my bike I either need full choke or half choke to start depending on how warm it is out. In November in the Northeast US, I need full choke to start it.
2. You do indeed have an issue with the starting circuit that needs to be sorted. Start with checking and cleaning the connectors in the headlight bucket.
3. Sounds good.
4. No spec on carbon buildup, but the exhaust will collect carbon over time, so this might be a false alarm. Worry more about carbon on the spark plugs more than carbon in the exhaust ports. Too rich of a mixture from the carbs can lead to excessive carbon on the plugs, so making sure your carbs are clean and setup properly would be high on my list.
5. If you have checked them as stated, it is probably just surface cracks. But keep an eye on them anyway.
And always needing the choke (which is really an enrichen circuit to add more fuel vs a choke plate which reduces air) is going to point to a clogged up or poorly adjusted idle circuit. So probably due for a good carb clean.
hey mike. sounds like we have same bike. mine is light blue. mine was a rare find. It had been stored long time in a garage. It was stored right because the owers gave it to a kid. and he put gas in it and it started. it was pretty mint when i got it. i got a kit for thecarbs but never used it. I just cleaned everything and put them back together. before i cleaned them it wouldnt idle.