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Tickover question 1 year 1 month ago #31190

  • PaulD
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My bike is setting down and running well finally with the water leak cured after replacing the bottom radiator hose “top hat” thingy. 
After a recent run out the tickover seemed a bit slow and lumpy (around 800rpm) so I adjusted the tickover knob and found that it took two full turns before it had any effect so it was obviously not touching the idle mechanism? When it did make contact the motor raced away until I backed it right off! Obviously something is out of adjustment but for the life of me I can’t figure out what?

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Tickover question 1 year 1 month ago #31192

  • Kawboy
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What you're describing is a perfect example of blocked pilot circuit (s). what you are describing is what happens when the idle of the bike is being supported on the main circuit because the pilot circuit is not able to keep the bike running. It's very difficult for the main jet to be controlled at low venturi air flow. When you start to open up the butterflies to increase the idle, as the low airflow in the venturi picks up the fuel starts to flow through the massive main jet (as compared to the pilot jet) and then the revs go way up, so you  close the butterflies and the airflow in the venturi goes down to the point that fuel stops flowing in the main jets and you end up with a high rpm / low rpm and can't get the bike to settle down.
I'm sure you're about to say "but I cleaned the carbs and paid special attention to the pilot circuit" and you wouldn't be the first to say that. What I feel is happening to most of those who have gone through this exercise is that your carbs were plugged up with varnish and you managed to clean a lot of it out, Even enough to get he bike running and moving fuel through the pilot circuit. Now there's fresh fuel in the pilot passages and it sits there until the next time you take the bike out. That fresh fuel has managed to dissolve more varnish that was left in the passages and maybe a few chunks of varnish have moved and blocked the idle or transition ports again.
I've done a lot of thinking about this because we heard from a few of the guys that they fight with this issue of blocked pilot circuits and we keep telling them that it's blocked pilot circuits and they think we are all nuts. In the meantime, they keep taking off the carbs and cleaning them out and the bike runs fine again until it doesn't and more posts "My bike won't idle anymore"
The other thing I think is really causing an issue si that Scotch and I believe Lacquer Thinner is the Bees Knees when it comes to cleaning out the pilot circuit and for whatever reason, lacquer Thinner here in Canada is not the same as Lacquer Thinner in Europe. Cellulose Thinner is not the same as lacquer Thinner. Xylene is a component of lacquer Thinner but Xylene alone will not work as well as Lacquer Thinner

This is a cut and paste " Lacquer Thinners are mixtures of different chemicals that dissolve lacquer. The specific composition of lacquer thinners vary by brand. However, the three primary ingredients are acetone, Toulene and methanol. These are the ingredients that dissolve the lacquer. Lacquer thinners often also include thickeners or waxes. This is because the main ingredients evaporate quickly. Waxes and thickeners prevent the thinner from evaporating before the chemicals have dissolved the lacquer."

Scotch and I have talked about our lacquer thinner and determined that even though we live 3000 miles away from each other, we both use Lacquer Thinner made by a company called Solvable


I really don't know what the bottom line is here other than to tell you that understanding what's happening when you have Idle or low speed issues is key to honing in on what part of the system is causing the problem. Carbs can be such a pain in the ass and some brands and models are worse than others, which explains why some guys dump certain models of carbs and retrofit other models that have a good track record.
It's going to be a battle if you're in the UK or Europe and I don't have a definitive answer for you as to what works best for a cleaning agent. Persevere,  you get it in the long run.
Hope this helps,
KB 
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Tickover question 1 year 1 month ago #31193

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Thanks KB, I have cleaned the carbs out MANY times and I even managed to buy the “tool” from Scotch and used that. I tried using cellulose thinners but as you say it doesn’t work so I managed to find some 2K lacquer thinners and have used that. Again as you’ve said the bike ran fine for a while and then started playing up again so it looks like something has dislodged and blocked the idle circuit up again. So it looks like the carbs have got to come off again and put scotch’s tool to work. Luckily I’m quite good at removing and stripping carbs now lol. 
thanks again 
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Tickover question 1 year 1 month ago #31194

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Maybe if you would be so kind to post your results after cleaning and reinstalling your carbs. It will confirm for us that the problem was indead the pilot circuit and that "another" cleaning was required.
Note- It's critical that you follow Scotch's instructions on using the tool step by step. Don't cut any corners. The whole process is critical in flushing out the debris backwards to the flow of gasoline through those passages. Something as simple as not removing the pilot jets will completely foul up the whole process. Things that have blocked the idle port and the transition ports will not flow out through the top passages if you fail to remove the pilot jets. 
It's also critical that your follow the sequence for the flushing. Mixing up the steps will also foul up the process. Take your time. Do it right. if you find you did step 7 before step 5, go back to the beginning and do all the steps over again. Think of it as pushing a piece of junk out a series of tunnels and there are 5 different exit points but they are at different entry points in the main tunnel. You push that piece of junk and it enters a passage but by skipping a step, you end up not following the piece of junk out the end of the tunnel.

The other thing that comes to mind is the fuel supply passages. So lets say you manage to clear out the pilot circuit and get things all back together and it's running fine. Now it's up to the fuel filter and a spotless fuel supply passage to keep the pilot circuit clear. I've had a set of carbs sitting on the bench for over a year and every time a problem comes up on the Forum, I go and study that set of carbs again. I've spent literally days looking at those carbs and even after all those inspections, I happened to look down the common fuel supply passage between the 3 carbs and the inside surface is littered with oxide / debris. Down right ugly. Anything that is not looking like fresh aluminum needs attention. 

As I mentioned previous, some carb models are more forgiving than others and these Mikuni BSW32's are problematic. They are a little more complicated with respect to the pilot circuit mainly because of the idle enrichment portion of the pilot circuit. It just adds to more passages where things can get trapped. Add this to the fact that the carbs are 40 years old and I'll suggest that a lot of KZ1300's have been dumped on the market because owners couldn't get them to run right. So if you bought one like this and are struggling to get it right, it's no surprise. All I can say is take your time and attention to detail. Don't overlook anything. You really can't especially with the Mikuni BSW32's.

KB
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Tickover question 1 year 4 weeks ago #31197

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OK an update on my tickover problem. I’ve spent the last two days stripping, cleaning, reassembling and setting up the carbs on my bike. There wasn’t any debris in the float bowls so I know the inline filter is doing its job. However using Scotches tool and following his instructions to the letter I was still getting small black particles after each flush? I printed the instructions out this time instead of trying to read them off my phone so maybe I didn’t do it correctly last time? I used one and a half litres of lacquer thinners to clean the three carbs and I kept flushing until the thinners were clean and no more bits came out. I reassembled the carbs and modified the link bars by silver soldering a small nut on the adjuster to make it easier to balance. I set the carbs up on the bench by adjusting the butterfly’s and shining a torch up the inlet to get them all completely closed. When I connected everything back up and started the bike the balance needed very little adjustment to get them equal. And now the tickover adjustment screw works as it should and when she warmed up the tickover settled down at 1000rpm nice and smoothly with no lumpiness. I’ve not road tested her yet but I’m quietly confident I’ve finally sorted it. Thank again for all the help 
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Tickover question 1 year 4 weeks ago #31198

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Fingers crossed you got it this time!
 
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