Single cylinder start up

[Theotherbrinks]

Hi to all this is my first time posting,got a problem and I’ve run out of ideas,I’ve got a 1983 XS650 Heritage with 16,700mls on it, bike starts on right side then comes in on both after 10 to 20 seconds, then runs fine .I’ve checked valve clearance, cam chain tension got a good spark, new battery,new high output coil, h/t leads and plug caps to match coil, tried both new standard plugs and Iridium ones, had the carbs in bits ultrasonically cleaned them new diaphragms even tried a new set of flat sides from Heidentuning (these do give it a bit more get up and go) also full exhaust as the std silencers were starting to rot inside, this is also where the coils, leads,caps and plugs came from, also ran a compression test both cylinders giving about 150 psi, I’ve run out of ideas any help on getting running right from startup would be of great help, had a XS650SE 40 odd years ago which was a points model,this one has the factory electronic ignition which I know zero about although it’s sparking well could this be the issue in some way? Many thanks

 

[Raymond]

Hi Theotherbrinks, welcome to the forum. Don't have the answer to your problem but when I start my XS, especially if it's been sat for a while, it sometimes starts on one side then the second cylinder chips in after a wee while. I usually put this down to the propensity of modern fuel to go gummy as it evaporates.

So, while I was thinking about possible carb or fuel issues, the random thought came to mind, do you open both fuel taps? If you are in the habit of only opening one tap, the fuel supply might lag behind demand for a few seconds until both float bowls are filled up? Just a thought.

But somebody on here sure to get to the bottom of it.

 

[gggGary]

Try putting it on the centerstand when you shut it off, see if the problem goes away. Another trial would be to remove and cap the vacuum line to the petcock, turn it to prime to run, back to on or reserve when parked.
Before the errant cylinder kicks in, shut down, pull the plug what do you see? Is it gassy, oily, or dry?

 

[Theotherbrinks]

Hi Theotherbrinks, welcome to the forum. Don't have the answer to your problem but when I start my XS, especially if it's been sat for a while, it sometimes starts on one side then the second cylinder chips in after a wee while. I usually put this down to the propensity of modern fuel to go gummy as it evaporates.

So, while I was thinking about possible carb or fuel issues, the random thought came to mind, do you open both fuel taps? If you are in the habit of only opening one tap, the fuel supply might lag behind demand for a few seconds until both float bowls are filled up? Just a thought.

But somebody on here sure to get to the bottom of it.

Thanks for the reply Raymond,regarding the fuel tap, it only has the 1 and it seems to work correctly from prime and the vacuum side,forgot to add in the post that I’ve had the bike 6 or so years and the things I’ve tried and changed have been over a period of time,I’ll get it sorted just looking for any ideas I’ve not tried.Regards Ian

 

[Theotherbrinks]

Try putting it on the centerstand when you shut it off, see if the problem goes away. Another trial would be to remove and cap the vacuum line to the petcock, turn it to prime to run, back to on or reserve when parked.
Before the errant cylinder kicks in, shut down, pull the plug what do you see? Is it gassy, oily, or dry?

I’ll try this,as I do think it’s something simple as when it’s running down the road it’s great,thanks gggGary

 

[Jan_P]

So an XS 650 with some problems never heard that before ( Joking )

What I would do is to check Voltage across battery everything off
then switch on se how much it drops
then measure with bike running charging Voltage

Then I would inspect the wiring to the Ignition witch special attention to the left side
connectors and make sure the grounding is there

What coil and was it the same with the old Stock aka matched with the ignition Box

It can take a while before both cylinders wake up but 10 - 20 seconds is to much For it to be carburetor related
I believe
It can be the box but the wiring service is a first and a must

 

[Theotherbrinks]

So an XS 650 with some problems never heard that before ( Joking )

What I would do is to check Voltage across battery everything off
then switch on se how much it drops
then measure with bike running charging Voltage

Then I would inspect the wiring to the Ignition witch special attention to the left side
connectors and make sure the grounding is there

What coil and was it the same with the old Stock aka matched with the ignition Box

It can take a while before both cylinders wake up but 10 - 20 seconds is to much For it to be carburetor related
I believe
It can be the box but the wiring service is a first and a must

Thanks for your thoughts Jan ,I’ll check these points out,the coil was a high out unit I got from Heidens in Holland had no effect ran the same as the std unit,many thanks Ian

 

[YamadudeXS650C]

Welcome to the forum Ian,
You've been offered some good diagnostic ideas; at the moment I don't have anything to offer.
I'm particularly interested in your results from Gary's testing.

Although it's irrelevant to your current issues, we always enjoy seeing a picture or two of the owner's bike.
BTW, I have an '83 and '82 in my stable, so I'll be watching with personal interest.
.
.

 

[5twins]

My '83 will sometimes do this on cold starts. Hot starts are fine, near instantaneous and fire both cylinders. It's not the petcock because I use Prime any time the bike has sat for more than a week or so, and it still does it. Since it's only a cold start issue, I'm leaning towards a choke problem. I've cleaned the choke jets in the float bowls several times so I'm pretty sure they're good. I'm thinking one of the feed pipes may be plugged. I've recently finished renovating some spare carb sets and hope to try them this coming season. That should verify if it's a choke issue.

 

[YamadudeXS650C]

My '83 will sometimes do this on cold starts. Hot starts are fine, near instantaneous and fire both cylinders. It's not the petcock because I use Prime any time the bike has sat for more than a week or so, and it still does it. Since it's only a cold start issue, I'm leaning towards a choke problem. I've cleaned the choke jets in the float bowls several times so I'm pretty sure they're good. I'm thinking one of the feed pipes may be plugged. I've recently finished renovating some spare carb sets and hope to try them this coming season. That should verify if it's a choke issue.

Now that you mention this, I recall that my '83 does this for maybe 5 to 10 seconds, just in the early spring.
With 7 bikes to get up and running after the snow melts, I've just ignored it.
.
.

 

[gggGary]

Might be the neoprene needle tip sticking to the float valve seat? Madness with VM34's (brass float needles) RH cylinder does it a bit. with separate chokes I can nurse it to life by manipulating that choke lever a bit til it's running consistantly. Then it's good til the next cold start.

 

[5twins]

I thought it might be a BS34 carb thing but my buddy's '80 starts cold easily and on both cylinders all the time. And now he has a refurbed 2nd set of carbs on there and it still starts easy.

 

[Theotherbrinks]

Welcome to the forum Ian,
You've been offered some good diagnostic ideas; at the moment I don't have anything to offer.
I'm particularly interested in your results from Gary's testing.

Although it's irrelevant to your current issues, we always enjoy seeing a picture or two of the owner's bike.
BTW, I have an '83 and '82 in my stable, so I'll be watching with personal interest.
.
.

Hi Dude, thanks for the welcome,I’ll start doing the testing shortly and put some photos up when the suns out that always makes things nicer, well better than the grey English weather we have at the moment Regards Ian

 

[jetmechmarty]

Did anyone mention swapping the plug leads? Swap them. Nothing should change. That should confirm a fuel issue.

 

[oberling]

I'm leaning towards carb issues. I have thought I did a great job cleaning carbs only to find them still plugged in some obscure spots.

 

[Theotherbrinks]

Hi overlong, thanks for your thoughts,I too keep thinking it’s fuel,but I have bought and tried a new set of flat side carbs still the same runs up on right side first when it warms up run really well, just that start up from “cold” I’ll keep plugging away and won’t let it spoil my fun .Regards Ian