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Hey Eric, Guys, and Gals!
First off I’d like to say I’m a huge fan!! I usually watch your videos, not because I need to repair something, but just to culture myself in this hobby of DIY repairs. The way you talk and explain things says you are a man with a passion, and an inspiration of mine. Now I finally have a question of my own to take to your forum!
It’s not exactly a car, but I have a 1991 Suzuki Katana 600. It has an inline 4 engine with each cylinder having it’s own carburetor. I’ve been trying to resolved this idling issue where when I blimp the throttle the idle goes to 3k and stays there a while then gradually goes back down. Sometimes it stays up there till I gradually let go of the clutch to bring it down at a red light. Once I use the clutch to bring it down it will stay at the proper 1.5k idle until the next throttle blimp.
I dumped a bottle of seafoam into the tank to see if it would improve the idle. Drove it empty, but has done nothing. I want to rule out any other problem before going to carb rebuilds, because hell I hate carbs, and doing 4 of them would be a nightmare. I’ve been reading around and people say that this kind of problem is usually related to having unsynced carbs. So I bought myself a carb syncing tool, warmed up the bike, then plugged it in. The results sort of surprised me, the needle was all over the place when the bike is at a steady idle of 1.5k as shown in this video:
https://www.youtube.com/watch?v=hupwo-w-ugE
Growing up in the world of OBD I have never done a diagnose from vacuum readings, so I’m a little lost as to what this means. I’ve watched my friends do this to their bikes before, but their needles didn’t move as much lol. Any ideas?
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Wow!
I’ll start by saying I know Jack-Diddly-Squat about cycles.
I would look into “Comparing” the differences between all 4 readings. You have 3 out of the 4 acting the same. Then you have #3. It just looks like the high peak is “Low” when compared to the other 3 cylinders.
Can’t say for sure what is going on…but that looks to be the weakest link. I’ll keep an eye on this topic—it’s quite interesting.
S-
I’m not a bike guy either, but I’ve synched multi carb and ITB setups on cars. The super-bouncy needles at idle is usually a sign of not having enough restriction in the vacuum lines. As a test, rev up the engine to about 3-4K, if the needles smooth out, then you need to add some restriction. You can do this by lightly pinching the line with some needle-nose vice-grips. Pinch enough to smooth most of the bouncing, not enough to completely eliminate it. There’s other methods I’ve heard of … but have no firsthand knowledge of them.
Good luck.
I don’t think the problem you describe is with the carbs themselves. I’d be looking to the throttle linkage. If you can, disconnect the linkage from the throttle and try and rev the carbs without it. If the idle comes down then, you know the issue is in the linkage.
As for setting up multiple carbs. I don’t believe that’s the way it’s done, or at lest, that’s not the way I’m familiar with. What I’ve seen is a tool that measurers airflow. You put it at the inlet of each carb and do what you can to match the airflow across each unit.
http://www.pacificcustoms.com/ac000124.html
Honestly, I don’t know what’s going on in the video. Perhaps you don’t have the gauges hooked up correctly. That said, I still think your issue is with linkage, not with the carbs.
[quote=”EricTheCarGuy” post=110450]
As for setting up multiple carbs. I don’t believe that’s the way it’s done, or at lest, that’s not the way I’m familiar with. What I’ve seen is a tool that measurers airflow. You put it at the inlet of each carb and do what you can to match the airflow across each unit.
http://www.pacificcustoms.com/ac000124.html
[/quote]
Yes that’s the tool us car guys use. But for whatever reason, a lot of bike shops seem to do vacuum balance synchronization, not flow rate synchronization. I’ve seen the style of gauge the OP posted, as well the type that have a series of mercury filled vials.
Hey guys, sorry it took me so long to give everyone an update. I’ve been busy riding my now fixed bike lol.
Anyways, I tried what McWicked stated and gave a little more restriction to the vacuum lines (by pinching them one at a time) to the point where the needle only vibrated between a couple tics. Worked perfectly! Found out #3 was way off, adjusted it, now the bike runs flawlessly.
Much appreciated everyone!
[quote=”fake_out99″ post=112979]Hey guys, sorry it took me so long to give everyone an update. I’ve been busy riding my now fixed bike lol.
Anyways, I tried what McWicked stated and gave a little more restriction to the vacuum lines (by pinching them one at a time) to the point where the needle only vibrated between a couple tics. Worked perfectly! Found out #3 was way off, adjusted it, now the bike runs flawlessly.
Much appreciated everyone![/quote]
I’m glad you got it all sorted out. Thanks for the feedback.
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