The adventure of a first bike and the young guy that owns it

it's fairly easy to check actually, if you take the carbs off and crank the engine around a few times with your hand on the cylinder intake holes, you should only feel it suck and never blow

no problem, the forum is for asking questions ;)

edit: if you got any crazy ideas due to the use of language in this post, I do not advise checking this with any other body part besides your hand
 
If you have a compression tester that would work to detect a smaller issue with the valves. I've never had a valve problem, but I would think in theory it would be possible to leak just a little bit too and you might have some pressure coming out of the spark plug hole even though there is a problem.

I'd definitely do a valve adjustment once the bike is very cold anyway. It should be done.
 
I actually already did the hand test, my friend who is helping me with the bike suggested it though and I did it though at the time I didn't really know what we were checking for, to see if that side was doing anything and it didn't seem to be blowing any air out. It felt the same as the working cylinder. Compression is above 120 (I don't remember how much) and really close if not exactly the same on both cylinders.
 
Great looking bike, bud! I have the exact same one. I got it in almost the exact same way (milage, price, etc.), and undoubtedly the same running condition (would start but not stay running, running on one cylinder, etc. I really like your new tank! Seeing it made me check ebay; I love the boxier look of earlier xs models.

You want your cylinders even and 150 and above. Re-test to confirm that you have 150 each. Search for "compression test how to" or something to that effect and find it on the site. Not sure what he was referring to when he said hand test.

You will certainly need to check your valves at some point, and if it ain't running, it ain't hot! Let it sit cold overnight, and test it before the sun hits it. Read like 3 threads on valve adjusment, and compare and contrast them all, look for the good tips and the trials and tribulations of others (not to make the same mistakes!)

You didn't say anything like "I installed an inline fuel filter...." so I assume you haven't yet. Do it. This is one less thing to go wrong in your tuning. Do it next, and before you clean your carbs again.

As for the current running condition - definitely lean. It is either an air leak (which bcware gave you the right idea on how to test for that) Or, it's your carbs. The carbs need to be meticulously clean. I personally don't think any other approach (except maybe boiling, which I don't like the idea of) can remove the "tartar" that has accumulated on the inside of your carbs aside from scrubbing. Pay special attention to the jets, because that is where the fuel is the business end of your carb. The pilot jet (the portion with the 16 tiny holes in particular) are one of the main places where grubby carbs can cause issues (especially with idle, starting, etc.).

How do you "scrub" these jets you ask? Try finding "wire gauge cleaners" at your local hardware or auto parts store. Not everyone has them, but they are a set of ribbed wires in different gauges from tiny to about the size of a virginia slims cigarette. These help to clean the inside of these jets really nicely. If you can't find them to buy, I've heard of people using guitar strings of various sizes, and just about anything stiff enough to get a nice abrasive scrubber for these tiny passages.

I believe you when you say you cleaned your carbs - but in this case, my guess is that the jets need more attention. Make sure you can see the inside of every passage. Hold them up to the light, and look for the inside to look smooth and continuous (not rough from a layer of plaque.)

Do your leak test before you pull them off, but if you pass the leak test, clean your carbs again.

Go ahead and change your old fuse box to a $5-10 blade type fuse box from your local auto store. The stock tube style is notorious for having the springs become brittle, leading to weird electrical demons.

After you got the bike running solid, you will probably have the mufflers go bad on you. The baffles become loose, and are non adjustable (they are tac welded in, and with the age, the connections soon breaks from vibration). Make sure you are confident that you get the bike running properly and confidently, then plan to replace your mufflers (requiring a re-jet of the bike, which is why I recommend you get all the adjustments right first. You need to know how the bike runs and sounds, pulses, etc before you go and change it drastically with new pipes). I used emgo shorties - as cheap and as loud as they come aside from maybe slash cut or straight headers. I may change them one day, but I love the grunt these give.

If your bike is like mine was when I got it, you will also find your charging system to be inadequate, or working improperly. Run the diagnostic located in the manual to determine whether it is or not. If it's not, then there are a few good threads you'll find if you search. This forum, good search skills, lots of reading (and some of my own trials and tribulations...) have got my bike from where you have yours now to where mine is now (running solid with confidence, moving on to fixing up the cosmetics and minor details). Bought mine with a bit under 8k on it, gonna hit 13k in a week or so. What started as a project for me became one of my most favorite bikes I've ever owned.

Cheers, and good luck!
 
It is really posts like the ones I've been getting over the past few days that make my glad I ended up with the xs400.

Thanks tombo! I really like that boxier look too and since the old tank needed replacing I figured why not. I found this one on ebay actually.
It's really nice to know someone else started out in the same boat and got a good reliable bike at the end.

The "Hand test" was to check for a bent valve. As far as the compression test I looked it up and I think I may have been doing it wrong. I had the other spark plug in and the throttle shut (and I didn't check to see if the choke was engaged)... So that will probably be first tomorrow.

Thanks again for all the advice I was starting to get pretty nervous but now I'm feeling like this is possible again.

More updates tomorrow
 
You can do it! :thumbsup:

Its not one big job- it's a bunch of little jobs. Reminding myself of that helps whenever I feel overwhelmed by a project
 
You might be able to take a bright telescoping led flash light while the bike is turning over and watch your valves go up and down to be able to tell if something is wrong.Its a long shot but worth trying.
 
Alright, sorry about the delay.

Did a compression test. Slightly warm, both plugs out, throttle open, choke shut. Sad to say: 120 both sides :/

It ran tonight... Much better when I did another full turn on the mixture screw. It was idling (pretty decently) at about 1500 and would die if I have it any throttle.

Next steps?

I'm thinking drilling out cap and cleaning left side mixture screw (I only have done the right so far to make sure I could do it successfully)

Checking/adjusting valves

Other recommendations for the next step are welcome and appreciated.
I have no idea how to fix a low compression problem.

image.jpg
 
You gotta do a compression test with a screw in type compression tester. Using the rubber typed jam style is not as reliable. Borrow one from the local auto parts store. If compression is still low, do a wet test (same thing, but after dropping a few drops of oil in the spark hole. If you notice a drastic increase, it indicates worn rings. Couldn't hurt to make sure valves are in spec before next test.

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The right plug looks to be oil fouled:( With low compression you most likely have bad rings.
 
There us still hope. I'd have to admit that it does look like oil fouling- but it could also be that that is the plug that isn't firing, and do it is fouled by being saturated in gas. I stand by my previous post to keep hope alive. Do your valve check, then compression test. If it isn't positive (150+) then wet test. If wet test improves compression significantly then you, as Chris stated, will need to do rings.

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I would be sad if it did need the rings replaced... But it would also give me an excuse to really clean the engine up :) plus rebuilding an engine is something I've always wanted to try and it will (hopefully) run great afterwards right?

That said, thanks for the hope tombo. I plan to try that out tomorrow so we'll see how that goes.

In the rebuild scenario where could I purchase new rings? I've noticed fairly often when I've ordered things some parts will be the same as what the bike already has and some are quite different (carb rebuild kit the gaskets and the main jet were right but the pilot jet was wrong). Any tips for places to get good stuff and things not to forget? (Also tips for cleaning the finned portions of the case)

Thanks again everyone. I'm learning a ton! If my bike ever fails once it's running at least I'll know what to look for.
 
local yamaha dealer for parts?

as for cleaning the fins i used some simple green and a brass wire brush followed by more green and a softer thin plastic brush.

Simple Green solution work great for cleaning my bike... use it over any oil stains on ur driveway and u might get lucky and have the green clear that away as well
 
There was a guy on ebay that was selling sets of standard rings for a good price ($52 shipped) I would try there also. If you need rings make sure to have the pistons and the bores spec'd out to see if you can still use them. Oversize piston and rings are almost impossible to find and cost big $$$:(
 
just a bit of advice on this hypothetical situation so far IF you end up doing a ring joc and your bores are in spec,use a good stone hone to make a good cris cross in the cylinder walls.
 
Sometimes you need an extra set of eyes to catch things...

My friend (whose garage my bike lives in) noticed that the oil was too full. So he drained some out and now it's at the proper level. He also noticed the fuel line wasn't allowing fuel to flow and fixed that.

Checked the valves... They were good.
Took off the carbs and cleaned them again (getting good at this)
This time I actually did it correctly. Set them up the same and right on all jets.
Bench synced them (which I had never done)
Started up. First kick. Both cylinders. Set idle just below 1500 with choke closed. Warmed up. Synced carbs with my snapple(tm) manometer (bench sync had it real close!) like it run a bit (just happy to hear it).

Rechecked compression... this time warm, both plugs out, throttle open, choke closed (as per service manual)... Over 145 both sides!!! Helps to not try and hold in the compression guage hold open the throttle and try and kick it on your own :)

Looks like PO replaced the old fuses but while it works. (For now) it's a little ghetto so I'll be replacing it with a blade fuse box soon.

Before it's ridable I need to figure out the cables. With my clubmans the cables are not working well. There's a customs shop down the street and I think I could get them to shorten cables for me but I don't know how long they should be... Anyone know from previous experience.

The1motorcycle show here in PDX is this weekend and im hoping to get to ride in :bike:
 
Great news!

The petcock only dispenses fuel under vacuum unless you have it on pri.

To much oil could be caused by stuck float valve in the carb, filling crankcase with fuel. smell your oil and keep an eye on it. Gas in crankcase will damage bearings

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