Z250 Single

Hey thats great to here Sham!
Pattons right, the float is the problem. Have you added any in-line filter to the fuel line? Maybe you have a piece of crud on the float valve. Or it could be the float itself could have a pin hole, then fills with fuel and sinks. you'll get it figured out. glad to here the bike runs after all.

Thanks guys.

Yeh I think its definitely the float/fuel levels.

So I was just checking it and noticed that the floats are .35mm off/different. Is it necessary to replace this?

I've replaced the fuel inlet needle even though the rubber was fine - the spring is much firmer.

sham wrote: ...think its definitely the float/fuel levels.
So I was just checking it and noticed that the floats are .35mm off/different. Is it necessary to replace this? I've replaced the fuel inlet needle even though the rubber was fine - the spring is much firmer. ....

If the .35mm is referring to a 0.33mm difference between fuel levels shown by the clear tube tests, then both levels are either okay or wrong. The level is supposed to be 2~4mm below the the float bowl gasket, as shown in the following illustration.



Differnt carb styles have their own peculiar float bowl drain systems.
The clear tube test relies on the carb's "drain" function, not the "overflow" function.
When clear tube testing, be sure the clear tube is being fed gasoline from the bowl "drain."

Don't worry about difference in firmness of the float needle spring.

Good Fortune!

Sorry I wasn't very clear, the two actually floats were not the same height, but I bent them back so they are now. The drain and overflow outlets are from the same hole, but the drainage hole feeds into the bottom of the float bowl, so I just have to unscrew the drain plug to use the "drain" function rather than overflow.

Ok so even though my tang is pushed up as much as possible, to lower the fuel level, it still sits 2mm above the top of the float bowl. Any suggestions on how to get it any lower?

Any possibility that the floats might be installed upside down?

Good Fortune!

Hey Patton, the floats are definitely installed right. I tried starting her up anyways. Here's the vid.

s1139.photobucket.com/albums/n560/shamja...current=884fdde5.mp4

Sorry, I can't work out how to imbed a video from photobucket, so the link is above.

So the bike started, with some issues. I'll try to have a look at it, but any suggestions to what the causes might be would be great.

1. Revs kept climbing as you can hear in the video, even when I stopped twisting the throttle. Is this just a case of a sticky throttle, or an incorrect idle speed?
2. Smoke started coming out from the right side of the engine (spark plug side) when it hit about 5k in revs. That's when I started looking for the kill switch. (found the light switch first...)
3. There was a burning smell afterwards.
4. There was a very very strong and constant vibration/rattle.

I had put some oil in the motor through the top of the valves after fixing the clearances. Could this have anything to do with the smoke etc? I'm not sure what the burning smell was.

On a side note, the carb didn't flood...

Thanks for the video Sham, good to here it running.
Now it sounds like carb issues still. The engine idle/ slow speed is definitely to high, so that needs to be corrected. It needs to be around 900-1200 rpm roughly. You need to check that the carb throttle linkage is not binding, and is returning fully. Also that the throttle mechanism in the carb can close fully when the idle speed screw is loosened. Also I know you put another carb holder/ manifold on, but you need to verify there is no vacuum leak. So the best way is first to get the engine speed down, to normal levels, then spray around the carb with a can of carb cleaner. If the Idle speed changes, engine usually will increase speed, then there is a leak that needs fixing.
This float with the Tang bent as far as it can go, and the float/ fuel level still high. If you take the carb off again and get a picture with the bowl off and the carb inverted, so we all can see the float and the carb gasket surface relationship, so a side shot picture. The Arms of the float are usually fairly close to parallel to the gasket surface. If way off I would suspect a wrong part, or a Needle and seat that is not holding back the fuel.

Hey Motorhead,

Thanks for all the info.
Yeh I checked the throttle cable and there seems to be enough free play, and it returns fine. I'm thinking it may be a diaphragm issue after another member from DDT suggested it, and looking through Dan's MC Repair Guide - supposedly holes in the diaphragm lead to creeping idle.
I haven't had a chance to check this yet but.
Also haven't checked the idle speed screw yet.

WIll take photos of the carb and floats and put them on soon. The O ring I'm using is from a z400 kit if I remember correctly (and the other parts replaced by the rebuild kit) but I have just found this site which seems to sell diaphragms and other carb rebuild parts for cheap - a diaphragm is under 30 pounds rather than the $120 or so I've been seeing.

www.nrp-carbs.co.uk/shop/index.php?route=common/home

Hey Sham, are you set up with this? Its from the first page of your thread.



If so this would be making your carb stock jetting too lean, and may well be the cause of the high Idle, and crappy running when you try to open the throttle.

Hey Motor Head,

Yeh I'm running the pod filter, but I changed the stock jetting to follow someone else's settings for their z250 (someone on the site, don't remember who). So the secondary (said to be in actual fact the primary) jet has been increased from 98 to 120, and the primary (read secondary) has been increased from 68 to 70. These figures are off the top of my head, but I believe that's what was said to have worked, and so that's what I'm running.

I checked the spark plug, and there was nothing, but I never engaged the bike in gear, so I'm not sure if that test applies.

So checked the diaphragm. I'm still not quiet sure if I have holes or not, a really long and close inspection under a bulb didn't seem to reveal any holes, but there were definitely lots of flecks of shiny stuff, kinda like glitter. I think I will check this under the sun on the weekend. I've tried to take some pictures to show the condition of the diaphragm, as even though though there didn't seem to be any holes, the rubber does flake off, even when I was stretching it, and is definitely quiet worn in some patches.

So not any closer on the creeping idle, the smoke or burning smell, but I think I may be onto something in regards to the high idle. I looked through the manual and found my current idle link and idle cam clearance is 0mm, when it needs to be between 1.5mm and 2.5mm. Too small a clearance here leads to a high fast idle.

Here are some pics of the float and float bowl too.

I think I'll try starting the bike on the weekend without the choke on just to see how it might react before making any changes.

So, it runs! No diaphragm issue after all, but sounds like carb/jetting issue now.

Had a friend over today to help out and test ride the bike. We found the smoke I was complaining of earlier to be coming from various parts of the exhaust, starting at the manifold. This, coupled with some very clunkly engine sounds - literally like things falling apart inside, led to a load more oil - the prescribed 1.4L was definitely not enough. After a couple more tries, the bike sounded a lot better, and stopped smoking from the manifold - now it smokes white from the exhaust, which, according to the manual means there's too much oil, but for now, I think that's preferable.

The idle with choke on is still incredibly high - around 4000 revs, but not as bad as before. The down side is, without the choke on, the bike struggled to idle. Got it there after it warmed up a bit, but it wasn't consistent and seemed to struggle.

My friend was able to ride it around the block a couple times and complained of the bike just totally loosing power whenever he tried turning the choke off. To me, this sounds like the bike is struggling with the pod filter I've fitted and the extra air that is bringing in. Even with the re-jetting I've done, using the sizing another member (forgot who) was using - 130 primary and 70 secondary, it sounds like its not quiet there. Will have to read up on jetting and carb tuning and see what can be done. Any tips?

Meanwhile the vibrations are still epic.

But we're on the right track.

Let me know if you spot anything in the vids that might identify more things.





Oh and here's the plug chop results - rich.

And lastly, a big thank you to all of you, for all the input and support. Wouldn't have been able to get it running without all your knowledge. I've really been very clueless.

Thanks.