Strange carb issues

Hi

Tried to start the bike after a long winter here in Sweden. Before it has never been a problem. But now it won't start.

The gasoline reaches the carburettors when I put the tap on PRI. But, it also starts to leak at the T-union, that is, the split that sits between the two middle carburettors and the tube that comes from the tap. It has done that before, but stops when I just move the union part around a bit. Now I have to turn the tap to ON or Res to make it stop. The gas reaches all carbs, since I can drain gas when unscrewing the drain screws.

I also checked the sparkplugs, which are dry, so it seems that no gasoline reaches the cylinders.

My conclusion is that it has nowere to go, since the gasoline doesn't reach the cylinders. But, since no cylinder gets gas, it has to blocked early in the system.

-What can cause gas being blocked from reaching all cylinders at the same time?
-Is there any gasket on the T-union part that needs to be replaced? In the repair manual it seems that it hasn't. Do I need to by a new one?
-Can I reapir this part without taking the carburettors apart from the bridge and/or taking them apart?

Any suggestions? I'never taken a carburettor apart before. Seems to be a lot of small things that can easely be destroyed or wrongly put together again.

I'd hope for a nice test ride today

/Martin

Martin,

Let me start with the standard reply:

Please create a signature line, and list your bike(s) there (model, year, mods) so that we know what kind of equipment you're working on. Makes a big difference to know which model you're referring to.

But with the generic info provided, I can give you some suggestions/answers.

First, the leaking T-Union. Many carb models have o-rings on each end of the T. Some "T"s are just one-piece tubes with built-in rubber seals. Whichever kind you have, you'll need to separate the carb bodies to inspect it, and replace if necessary.

You mentioned that you have a repair manual. The procedure for dismantling the carb assembly should be explained there. Don't be intimidated by the apparent complexity of the carbs. Just take your time, follow the manual, and clear a nice big space on your workbench so that you can lay everything out in an organized way, and not lose any small parts. You may want to also take several pictures along the way, just in case you need a reference when reassembling them.

Now, let's talk about fuel getting to the cyls. If you're getting fuel to your bowls, but not into the engine, then it sounds like you've got some clogged passages/jets in your carbs. Remove your float bowls and see if you have any sediment or gooey varnish in the bottom. Do you use an inline fuel filter between your petcock and carbs? If not, it's a good idea to install one.

Since you're already going to be separating the carb bodies to replace the T-union o-rings, This is a good time to also do a thorough cleaning of your carb interiors.

There are several ways to approach this, and there are many threads here with good suggestions about carb cleaning.

When I do a deep clean on my carbs, I completely disassemble all the parts, paying special attention to remove anything non-metalic (o-rings, diaphrams, gaskets, etc.). Before removing the mixture screws (if applicable your model), turn the screws in all the way until "lightly seated", and count the number of turns. Write this number down for each carb so that you can return it to its original setting when reassembling.

After getting everything apart, I then soak all the metal pieces in a carb dip solution. I don't know about the availability of this stuff in Sweeden, but in the US, you can get it at an auto parts store. It comes in a 1 gallon metal can, and includes a metal tray that you can put the parts into, and lower into the solution to soak.

After soaking for a while, I remove the parts and flush with water. Then I use carb cleaner (in a spray can with a plastic nozzle tube) to spray into every passage opening I can find. Be sure to wear appropriate protective gear (especially gloves and glasses). As you spray into one hole, the fluid should squirt out somewhere else. And sometimes that "somewhere else" is right in your face. :blink:

Some of these passages are very tiny, and may not be obvious to see. So inspect the carb body carefully to make sure you have cleared EVERY passage. Do the same for all the jets, making sure that they are completely unblocked. Some people use fine wire to clear blocked passages/jets. Be very careful if you do this with jets. You do not want to distort the jet orifice at all, and metal wire can do this if you're not cautious.

After squirting carb cleaner through the passages, I follow up with a blast of compressed air to remove any remaining fluid or particles.

Inspect your float valve needles to make sure they are not worn out, and replace if necessary. Also replace the bowl gaskets (if necessary) and it's a good idea to replace any o-rings--especially the tiny ones on your mixture screws (if applicable to your model).

After reassembling everything, you'll need to re-synchronize the carbs. The procedure for doing this will depend on your specific model, and the type of equipment you have, or are willing to buy/make. You should be able to find instructions here on KZR, or in your manual.

Good Luck.

Wow... that about covers it - good job!

You can do it, Good luck!

I would spray carb cleaner on the air filter(s) and see if she fires enough to get the fuel flowing, if not follow the outlines above. Carb cleaner is rough on motors so do not over do it but its worth a try, especially if you have never pulled carbs

Thanks everybody!

I have a KZ650 B2, -78.

Great explanation about how to clean the carbs. Wow!

I read that the t-junction gasket can function again after it has being soaked over the night, so I will check this again first before taking it apart.

Since it is spring and I want to go for a ride as soon as possible, i seems like a good idea to give the carb cleaner gas through air filter a try first. If I can find carb cleanar as gas. And save the complete cleaning to next winter...

Or, if nothing works I hope it will not take me so long to clean the carbs. Any parts I could try to clean first, so that I don't have to take the whole carbs apart and readjust it/them?

Also, would it be a okej to use paraffin oil or thinner to soak the parts in and then use compressed air in spray can?

/Martin

Martin, I understand the desire to take some short cuts to get out on the road, I really do.

But the difference between having clean, properly adjusted carbs, and taking half-measures, just enough to get it running can be quite significant. You will be amazed at the difference it can make.

Obviously, you can decide for yourself how best to proceed. But my suggestion would be to sacrifice 1 or 2 riding days to get the carbs properly cleaned and adjusted, then enjoy a whole summer riding a properly functioning bike.

"Paraffin oil" is what we call "Kerosene", right? I think it is okay to soak in Kerosene, though I've never used it. I'm not sure how effective it would be at clearing blocked passages. But maybe combined with the compressed air, it might work. Can you get carb cleaner in a spray can (with the attachable plastic nozzle tube) there? If so, that would be best for clearing jets and passages. But make sure that you first remove any rubber/plastic parts before spraying with carb cleaner, as the cleaner will dissolve/degrade them.

You mentioned "soaking" your T-union. What are you planning to soak it in? Be careful not to destroy it with something that eats rubber/plastic.

You're absolutely right that it's best to do it well from the beginning. That's how I usually like to do it.

I'm just worried that I will have to order new gaskets, o-rings, etc, which would perhaps be difficult here in Sweden. If they don't have it (old bike), it may take several weeks for them to order from abroad. Maybe I could by it online from Z1 Enterprise or some other store more quickly.

Great tip about removing the rubber parts before soaking the parts in carb cleaner.

With soaking the T, I meant that rubber might have been dryed during the winter, and now soaked in gasoline for some days, it might expand by itself a bit and function again. I will check this out tonight. Someone told me I could try using teflon tejp. Or I would have to order a new T part, which would probably take a while.

If the T is working again, is it possible to clean the carbs without taking the carbs off the bridge? Or do I have to separate the carbs from each other before taking them apart. I do have the Haynes manual, so I intend to follow that. But sometimes people come up with more simple procedures. By the way, since it isn't even starting on idle, is it some part of the carb (jet, hole, etc) I could focus especially on, that might be the main problem?

Regarding the tuning and sync after putting the parts together. Since I don't have any advanced measuring tools, is it possible to get it right by doing it mecanically?

/Martin

Martin,

Yes, you can give the carbs a pretty good cleaning without separating the carb bodies. It just makes it more difficult to soak them in a carb dip can, since they won't fit (unless you have a large dunk tank). But you can still open them up, remove all the jets, and spray carb cleaner into all th passages and clear them with compressed air.

The problem is that in order to remove the T-Union, you WILL need to separate the carb bodies. I'll say it again, don't be too intimidated by this. It seems more complicated than it really is. I remember that I too was hesitant to break them apart. But after doing it, I realized it wasn't really a big deal.

As for sync'ing the carbs afterwards, if you don't have a set of special vacuum gauges, or a special sync tool, you can make your own very simply and cheaply. It is explained in the document found here: kzrider.com/index.php?option=com_docman&...d&gid=187&Itemid=108 .

You can also do what they call a "bench sync" first. This basically involves making adjustments to the carb slides while the carbs are off the bike, and using 4 same-diameter drill bits (or wire) to measure the slide openings and adjust until they are the same. This procedure is explained here:

kzrider.com/index.php?option=com_docman&...d&gid=193&Itemid=108

The "bench sync" will get you close. But you should still do the live sync with the engine running using the manometer to get the synchronization perfect (or close to it).

Skyman wrote:

Martin,

Yes, you can give the carbs a pretty good cleaning without separating the carb bodies. It just makes it more difficult to soak them in a carb dip can, since they won't fit (unless you have a large dunk tank). But you can still open them up, remove all the jets, and spray carb cleaner into all th passages and clear them with compressed air.

The problem is that in order to remove the T-Union, you WILL need to separate the carb bodies. I'll say it again, don't be too intimidated by this. It seems more complicated than it really is. I remember that I too was hesitant to break them apart. But after doing it, I realized it wasn't really a big deal.

As for sync'ing the carbs afterwards, if you don't have a set of special vacuum gauges, or a special sync tool, you can make your own very simply and cheaply. It is explained in the document found here: kzrider.com/index.php?option=com_docman&...d&gid=187&Itemid=108 .

You can also do what they call a "bench sync" first. This basically involves making adjustments to the carb slides while the carbs are off the bike, and using 4 same-diameter drill bits (or wire) to measure the slide openings and adjust until they are the same. This procedure is explained here:

kzrider.com/index.php?option=com_docman&...d&gid=193&Itemid=108

The "bench sync" will get you close. But you should still do the live sync with the engine running using the manometer to get the synchronization perfect (or close to it).

Good stuff! The previous posts pretty much cover it, good luck. I know it doesnt help for gaskets, but you can probably find an O-ring kit at a hardware/auto parts store that includes the sizes used in the carbs/jets. Try and repair/re-use the gaskets as best you can if they are damaged and wait until some new ones can arrive in the mail. I would try and do it right the first time... I pulled my carbs last week and did a quick cleaning without pulling them off the rack and am going to be going the whole dismantling route this weekend... Lesson learned, if you're going to go through the trouble of pulling them and cleaning them, do it right the first time so you can be sure that they are clean and everything is flowing. Also - you cant get to the enricher (choke) circuit without pulling them off the rack...


I was planning on doing a bench synch after giving my carbs the full treatment, but with that handy (cheap!) little device (and some delicious snackfoods) I might just have to try vacuum synching in the near future as well.

Cheers!

Fantastic!

The T-Union seem to work allright now. No leak! But still no gas reaches the cylinders, still dry.

I do have a poor battery, but since the starter clutch doesn't work so good (the starter slips almost directly), I normally use the kick starter to start the engine from cold. It worked great last year. As far I know a poor battery shouldn't cause the gas not reaching the cylinders. Or??? I do see sparks when using the kick, even though they don't seem to be that strong. I will buy a new battery this weekend. Best to rule this out before taking the carbs apart. I even tried with connecting another battery with the engine going and used the starter. But due to the poor working starter clutch, it slips almost directly.

I will also do as you, skyman, suggest. Use carb clean spray, let it work and then take it to a do-it-yourself station, where they have strong compressed air (not can version). And finally clean it from carb cleaner. And thanks, sft1662, for the gasket tip.

Thanks also for the tuning and sync recommendations.

The strange thing is that all four carbs stopped working at the same time. I did try using start gas through the air hose, but nothing happened. May it be something else???

Big thanks for discussing this.


/Martin

Has compression test been performed? Decent compression is required for suction through intake port which is needed to pull fuel mixture from carb into combustion chamber.

See below for cleaning carb pilot circuit.

Good Fortune!

[Click on image to enhance view.]

Thanks for the picture! It will definitely help.

Yes, i did compression test two years ago. And the bike worked normally last season. I don't think the compression rate can suddenly drop during the winter storage. I also normally drain the carbs by letting the bike run until it stops before winter storage. This winter i didn't, so perhaps it is this. I'm still suprised that it caused all four carbs to be blocked.

Can a poor battery cause bad compression, and therefore bad suction, even though I use the kick starter?

Martin