1983 Yamaha Maxim Xs400 won't rev?

[willem]

try to put it back as best you can. And yea that can cause problems now, good luck with that

The way to check your clutch plates for functionality, without being able to run your bike in gear, is by walking with your bike as I mentioned before. Just pull in the clutch, put the bike in 1st and walk with it. While you're walking, let the clutch go and the rear wheel should lock up. Pull in the clutch and you can walk again.

If your plates are bad, your rear wheel will not lock up. Easy.

To check your gears, try to do a running start. Push the bike when it's in 2nd with the clutch pulled in, then when you've got some speed, jump on the bike and let the clutch go. The bike should turn over 2 or 3 turns before you come to a stop, depending on how big you are and how fast you ran. As I said, this is a way to get the bike to start, so don't be surprised if you take off Do the same in 3rd gear, and it should be easier to roll through the compression. Test every gear like this, it should barely cost any effort to push it forward in 5th.
If you feel like it gets easier to push the bike through the compression every time you go up a gear, they're good. If there's something wrong, you'll notice something being off.

 

[chrisd1984]

heh yeah was thinking of bending the tang and making the one that sits lower match the one that wasn't touched, think that is a safe bet? Probably will also change all the fuel again and possibly through on an external fuel filter as well. Really hoping the jets won't need resetting or something...all I know if that it worked fine before and since cleaning the carbs the first time the performance has improved a little (but still stalls when engaging first gear)

 

[Lou Ranger]

... (but still stalls when engaging first gear)

You are pulling the clutch in when you engage first gear, right ....

 

[chrisd1984]

yeah...start the bike up with the clutch in, shift to first and engines stalls. Sometimes it even stalls just sitting in neautral after starting it up, I watch the revs decrease over 10 seconds until the engine fully dies

 

[willem]

clean those carbs!

 

[chrisd1984]

yeah ill get er done this weekend

 

[chrisd1984]

Hey so took out the carbs again and REALLY cleaned them - even had another friend take a look, every passage is spotless. Also changed all the old gas to newer ethanol free gas and changed the fuel filter and fuel line. Also checked the gears as well and they're fine and cleaned the air filter again.

Really doesn't seem to have made things too much better though...basically it does run intermittently. Example, I started it last night and if you rev the throttle over 4000 rpms and switch into first gear, the bike will run but will run kind of crappy. But if you start the bike and leave it in neutral, the rpms will gradually decline until the bike stalls after 10 seconds or so. Also, the bike doesn't always turn over either - a lot of the time I'll be pressing the start button and trying the different petcock positions and it just won't crank. Shouldn't it crank every time?

Also checked the plugs and they're not flooded with gas. It feels like the bike isn't getting enough gas or that there is some other error in the ratio of air vs. gas. Think I may have also heard a few clicking sounds from the crankcase when it was running while giving it throttle and driving. Any ideas? May just have to rbing it to a emchanic but the ones around Toronto seem kind of useless.

 

[willem]

Yes it should crank every time. Check your battery voltage. If your electrics are bad (which it now sounds like they are) you're gonna stall the bike as well.

Also, turn your idle mixture screws out to about 3 turns and see what happens. Play with them a little. Also adjust your idle screw (the one which is at the throttle on your carbs) to get a bit higher rpm at idle.

 

[chrisd1984]

Hmm would you be able to provide more instructions or possibly a photo of where the idle mixture screw is on the carbs? I know where the idle screw is but couldn't locate the mixture screw...do you think this could correct the revving issue? I just want it to run like it used too. When I first had the bike a few months ago it would set in neutral and never decrease in revs until stalling; now I have to give it extra juice just to make it turn over.

There also seems to be a small leak in where the exhaust connects into the crankcase, I notice a bit of gases escaping at the front of one. Couldn't this effect the revs too and engine performance? I wanted to try tightening it but unsure of what tool to use...it looks like a large hex tool? And I'm not even sure if it's just loose or broken somehow...there is a leak though for sure.

One last thing that is a huge issue.....it seems when I have the bike in neutral now, sometimes it revs up like crazy without me even touching the throttle. It will just sit there and increase in rpms....this is dangerous as you can imagine. It even happened when I rode it for a second. The throttle cable seems fine though. Could this be from a malfunction in the carbs or an air leak somewhere or that exhaust leak or the idle screw? Sorry I know I ask a lot of questions but really hoping to get riding it now that the weather is nice

 

[Lou Ranger]

.... One last thing that is a huge issue.....it seems when I have the bike in neutral now, sometimes it revs up like crazy without me even touching the throttle. It will just sit there and increase in rpms....this is dangerous as you can imagine. It even happened when I rode it for a second. The throttle cable seems fine though. Could this be from a malfunction in the carbs or an air leak somewhere or that exhaust leak or the idle screw? Sorry I know I ask a lot of questions but really hoping to get riding it now that the weather is nice

I have not had the problem, nor any first-hand experience with air leaks, but I read last year about a bike that would start over-revving after it warmed up. Turned out to be an air leak in the air intake which would get worse when the engine warmed up - presumably metal expansion widening or narrowing a crack.
Have you done the standard test for this (spraying carb cleaner or propane on the intake tubes)?
Apparently if there is a leak the revs will change.

As to your intermittent starting, if your battery tests okay, then maybe it's a short in the starter button. My sr250 used to do that and it turned out to just be an intermittent connection in there somewhere.

 

[chrisd1984]

hmm but if the butterfly valve is closed wouldn't that keep out any excess air from entering the carbs from the air intake?

Also it seems that some of the air escaping from the exhaust leak effects the performance: the engine kind of sputters while in use. Would you have any idea what type of tool to use to adjust this?

I did try spraying some chain lube (was all I had at the time). Didn't work out too well so will use something more combustible today

 

[Lou Ranger]

hmm but if the butterfly valve is closed wouldn't that keep out any excess air from entering the carbs from the air intake?
Also it seems that some of the air escaping from the exhaust leak effects the performance: the engine kind of sputters while in use. Would you have any idea what type of tool to use to adjust this?
I did try spraying some chain lube (was all I had at the time). Didn't work out too well so will use something more combustible today

The butterfly is internal and would have nothing to do with an air leak affecting the mixture going from the carb to the engine.
Spraying carb cleaner is a diagnostic technique only. If there is a change then there is a leak and you can stop wasting time and money on other things until you find and fix the leak. How you locate and correct a leak is a separate project.
It's good to know that there is not a leak too, but I suspect that it is a mixed blessing since it means it won't be something simple.
Chain lube would not have been my first choice to test for a intake leak. Hope you got it all cleaned off.

 

[chrisd1984]

yeah I'll see if I can find one. hah yeah chain lube was a bit of a nuisance to clean off but got it done.

Heard it could also be the clutch causing the revving issue but we'll see

 

[chrisd1984]

yeah so fixed everything on it and had a mechanic took a look at it. Theys aid everything is good but I'll need new clutch plates, clutch barrings and clutch cable soon. I suppose Yamaha wouldn't still carry these and I'll have to find someone parting out?

 

[Lou Ranger]

Did the mechanic explain to you how clutch parts have anything to do with the engine failing to rev? You may well need them TOO, however, they sound completely unrelated to me.

 

[chrisd1984]

Hey so got the bike back tonight after the mechanic said it was starting and running fine at his shop and it doesn't seem to be starting for me.

Is there some sort of sweet spot for starting a 1983 Maxim or perhaps I'm missing something?

I keep it on the top setting on the petcock, push the clutch lever all the way to the right, hold the clutch in and press the start button for 2 seconds. (there is plenty of gas in the tank) And it usually just tries to start but doesn't run. Could the mechanic have been doing it another way? It seems whenever I bring it back to them they always say it's running great and it rides everywhere but when they drop it back off at my place, I can't crank it and the few times it does crank the revs are uneven and the engine usually stalls. Is there some secret with using the fuel enrichener that perhaps I'm missing?

Should I usually wait a few minutes before trying to crank it again and should I wait for the red oil pressure light to go out for an easier start? I just figured that it should start everytime and there shouldn't be all of this trouble.

 

[Lou Ranger]

... push the clutch lever all the way to the right, hold the clutch in and press the start button for 2 seconds ..
.. and should I wait for the red oil pressure light to go out for an easier start? ...

If by clutch lever you are actually talking about the choke lever, then to the right is wrong. When the engine is cold, pull the lever all the way to the left. All the way right is for when it's warm and you are ready to ride.

I don't think the red light goes off until the engine begins to run and pump oil, so don't wait. If it stays on before it starts it's normal. But if it stays on AFTER it is running, you have a problem

 

[chrisd1984]

Ok thanks. So start it in the left and when it's started, pull it all the way to the right?

And is it normal for rpms to fluctuate a little when idling? It lowers and then raises...is there anyway to finetune this?

Also just noticed my carbs seem to be leaking gas): Everything seems tight though....not sure what that's about

 

[willem]

You start it with the choke lever all the way to the left, and when it's running you leave it there for about a minute. When it's really cold outside you'll need it for another minute.

If your idle is not stable there's probably some dirt in your carbs, or your carbs are out of sync, or you need to adjust your idle screw, or your throttle cable is doing something weird.

Leaking gas is a sign of your floats not doing their jobs. Tap on the carbs with a rubber hammer, sometimes that helps already. But the real solution is to open them up, clean them and adjust the float height. Check around your float needle if that's working well, and check the rubber o ring there. Consider replacing it.

 

[chrisd1984]

Ok. where exactly is the idle screw on the carbs and how will I know if it's been properly adjusted?

I'll try banging it a bit to see if that helps with the leak at all.