Failed start

[acebars]

I only just managed to get around to the TX650 I bought months ago.

Anyway cleaned out oil filters (although they needed really no cleaning), put new oil in, new fuel pipes etc. charged the battery.

Cleaned the carbs with carb cleaner and an air compressor, unscrewing everything I could as I went along. Put new floats in with correct height etc.. This was more than enough to start most bikes in the past (this is my first XS650).

To cut a long story short put them on the bike tried to fire the bike up and after minutes of trying the electric start I failed to get it started. I seem to be missing the choke parts to keep the choke engaged on the left carb, but even opening the throttle fully failed to start the bike.

I checked spark its good, fuel was in the carbs, no overflowing so I presume float valve is ok.

I didn't mount the air filters but couldn't imagine they'd stop the bike starting.

My carbs were very tatty to start with, I couldn't remove the pilot jets due to corrosion and several parts were difficult to remove, but diaphragms are good.

Could it be that I need to give the carbs a good clean again? I'd usually go for a lemon boil at this point which has usually sorted out anything like this in the past.

First time I've been stumped like this with a new old bike, usually I get some life signs even if the bike doesn't start indicating I need to go over the carbs again but I got nothing at all just turning over with the electric start.

 

[timbeck]

I think I would use a quick shot of ether. I know ether is a pretty violent fuel to hit an engine with, but if you can get it to fart at least that tells you ignition /spark are within range. At that point the carbs are the most likely suspect. tim

 

[weekendrider]

If the pilot jets were too gummed to remove, chances are the whole circuit is plugged?
If you spray aerosol carb cleaner in the pilot do you see it coming out the holes in the throttle body at the throttle plate?
It could be you will need to remove the mix screw and spray from that end trying to clear the pilot jet?

 

[retiredgentleman]

+1 what weekendrider said.

You must have the choke working.....................there is a very small fixed jet in the bottom of the float bowl, that must be clear to allow fuel supply for the choke circuit.

The carbs need to be surgically clean. The pilot jet must be clear.................its a tiny orifice so it plugs very easily.

 

[jd750ace]

With most, you will need a filter or a hand over the intake to start once you have the carbs cleaned out good. CV carbs like a still air supply. They are quite different from old style butterfly carbs in that regard.

 

[acebars]

If the pilot jets were too gummed to remove, chances are the whole circuit is plugged?
If you spray aerosol carb cleaner in the pilot do you see it coming out the holes in the throttle body at the throttle plate?
It could be you will need to remove the mix screw and spray from that end trying to clear the pilot jet?

I don't remember as I cleaned them a month ago. I did remove the mix screw and do it from that end.

With most, you will need a filter or a hand over the intake to start once you have the carbs cleaned out good. CV carbs like a still air supply. They are quite different from old style butterfly carbs in that regard.

Thanks guys..

Ok I'll put the filters on next time.

I'm going to boil the carbs up in a light lemon solution, I've found it to be similar in action to ultrasonic will loosen it all up and I should be able to get the pilot jet out then when its hot.

I'll give it a good going over and report back.

You must have the choke working.....................there is a very small fixed jet in the bottom of the float bowl, that must be clear to allow fuel supply for the choke circuit.

There is only a choke on the left carb, I will sort it but have been able to start all my bikes by throttling them if the idle system is not working in the past.

 

[Bucko]

Are your plugs getting wet?you could always try a little petrol down the plug holes!

 

[acebars]

Are your plugs getting wet?you could always try a little petrol down the plug holes!

I'll try it next time.

Got the pilot jets out, hopefully won't have to boil the carbs and will get away with just carb cleaner and an air compressor.

I forgot to add my bike is on its side stand as I don't have a mainstand, I can't imagine this affecting starting? It shouldn't should it?

 

[retiredgentleman]

I don't remember as I cleaned them a month ago. I did remove the mix screw and do it from that end.



Thanks guys..

Ok I'll put the filters on next time.

I'm going to boil the carbs up in a light lemon solution, I've found it to be similar in action to ultrasonic will loosen it all up and I should be able to get the pilot jet out then when its hot.

I'll give it a good going over and report back.



There is only a choke on the left carb, I will sort it but have been able to start all my bikes by throttling them if the idle system is not working in the past.

The choke is very important on these bikes. Since you only have it on one carb, you definitely want it to be working. There should be a tube that directs the rich mixture from the one (choked) carb over to the other (non choked )carb.

 

[acebars]

The choke is very important on these bikes. Since you only have it on one carb, you definitely want it to be working. There should be a tube that directs the rich mixture from the one (choked) carb over to the other (non choked )carb.

Ah yes there is, I unscrewed the 3 screws holding the choke assembly onto the carb but it is stuck together and i can't get it off. I think boiling the carb will sort it and get it off so I can clean inside.

 

[retiredgentleman]

Ah yes there is, I unscrewed the 3 screws holding the choke assembly onto the carb but it is stuck together and i can't get it off. I think boiling the carb will sort it and get it off so I can clean inside.

Don't forget to check that the small jet in the bottom of the float bowl is clear.

 

[Pasiv65]

Hi!

I´m following this topic with big interest, because I also finally got the bike to the point where I´m trying to start it. Yesterday evening I tried it the first time, but unfortunately with no success... Only few backfires from exhaust pipes.

I´ve been searching the forum, and I think that I should check first the cam timing and then move to the carbs.

What do you think, how harmful it is to the engine to make these failed start efforts again and again? I´m thinking about the oil circulation and the starter motor´s lasting.

Pasi

 

[hard_y_rd]

Did you try starting it with the throttle slightly opened? I know that is not the proper way of starting these bikes but that is the only way my 73 will start. My carbs were cleaned but my choke seems to have the same symptoms as yours. I'm going to have another go at the carbs. Starts no problem with a roll on the throttle.

 

[Pasiv65]

Yes, the only signs that the bike would start came when I slightly opened the throttle. I don´t know why, but when doing this the engine sounded to turn easier and faster.

Pasi

 

[retiredgentleman]

Hi!

I´m following this topic with big interest, because I also finally got the bike to the point where I´m trying to start it. Yesterday evening I tried it the first time, but unfortunately with no success... Only few backfires from exhaust pipes.

I´ve been searching the forum, and I think that I should check first the cam timing and then move to the carbs.

What do you think, how harmful it is to the engine to make these failed start efforts again and again? I´m thinking about the oil circulation and the starter motor´s lasting.

Pasi

If your bike has 2 coils, they fire alternately every 360 degrees rotation of the crank. You may have both cylinders firing on the exhaust stroke. Swap over the plug leads and see if the engine will then fire correctly. If it does, then swap over the wiring that connects the coil to the points, and return the plug leads to normal.

 

[Pasiv65]

Thanks again, you were absolutely right! Yesterday evening I opened the ATU cover, and started thinking that maybe I have installed the timing shaft 180 degrees wrong. So I took the bob weights off, turned the shaft half a turn, and put the weights back. After that the engine started just fine! It had been firing at exhaust stroke. So I did what you suggested but little harder way

Pasi

 

[retiredgentleman]

Thanks again, you were absolutely right! Yesterday evening I opened the ATU cover, and started thinking that maybe I have installed the timing shaft 180 degrees wrong. So I took the bob weights off, turned the shaft half a turn, and put the weights back. After that the engine started just fine! It had been firing at exhaust stroke. So I did what you suggested but little harder way

Pasi

Yes, that will work as well

 

[acebars]

Glad you got it fired up

Have boiled up my carbs with a weak lemon solution, then completely cleaned them again with carb cleaner and an air compressor. It is for sure nice and clean now and rebuilt.

Hopefully will get a moment to try the bike again tomorrow.

 

[weekendrider]

Did you remove the throttle shaft seals?

 

[acebars]

Did you remove the throttle shaft seals?

You mean on the carbs right?

From experience I prefer not to remove these at least not initially, I did it one time on CB450 carbs and it ended up causing an air leak through one of the throttle shafts, it was incurable and was reported by other users of such carbs.