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Discussion Starter · #1 ·
I have rebuilt my carbs and have replaced my slow jets from the stock 40's to 45's. Did that because after doing the exhaust hole saw mod, my pilot screws were out to 4 1/2 or so turns. I have sync'd my carbs 2 times and each time it seems the adjustment changes. After syncing last, I since hooked up my homemade meter and the level is now off by about 8 inches.

To achieve a decent idle I have my rear cylinder carbs pilot screw at 3.5 turns out and the front cylinder carbs pilot screw out 2.5. The front cylinder pilot screw has no effect out past the 2.5 turns.

Also now with my pilot screws set as they are, when starting the engine cold, the choke makes it too rich to use and the bike will idle super slow till warm.

The bike runs good at all throttle responses with no hesitation and minor exhaust backfiring on decel. I just want it to idle nice and smooth. It sounds like it is misfireing occasionally only at idle.

I am used to 4 cylinder bikes and they run smooth. This is my first v twin. Should the v twin idle as smooth as a 4 cylinder.

Let me know your thouhts on what I should check.
 

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I'm not so familar with the older bikes, but a 4 is going to idle much smoother.
I very rarely use my choke for cold starting, I just give my idle screw a half turn till its warmed up. I went up one size on my pilots.
 

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well I dont think you should be a full turn diference on the idle mixture screws, I'd get them pretty close 2.5 front and 2 3/4-3 turns on the rear, and resync them.
But I would first check to make sure you have no vacuum leaks and the boot clamps are tight, check your valve adjustment lately?
 

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Discussion Starter · #5 ·
I have suspected vacuum leaks but I have not detected any using starting fluid around the boots.

I though after rejetting the pilot jets, I would only be out 2.5 turns at most on the pilot screws.
 

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I have suspected vacuum leaks but I have not detected any using starting fluid around the boots.

I though after rejetting the pilot jets, I would only be out 2.5 turns at most on the pilot screws.
does the rear idle nice when you get it to 3.5, I personally back them out to get the best idle then turn them in 1/4 turn
when you had the carbs apart, did you remove the mixture screws, and clean out those passages as well, its possible the rear may be a little dirty, are the o rings and washers installed on the mix screw in good shape. did you clean out the passage for the pilot jet in the carb base when you had it apart?

And tight valves can cause problems, just keep that in mind.
but did you have any problems B4 the holesaw mod and the carb rejet?
Any other vacuum hoses running to the carbs?
 

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The valves are Hydraulic in this bike, no adjustment.
The A/F screw(s) is not what sync's the carb, do you know that?
They are "basically" fine adjustment of idle/closed throttle.
I bet a hundred bucks you can use choke AFTER bike is running to increase idle to close to 3000 RPM if you want.

I apologize if indeed you do understand where the sync screw is, it seems by reading the post that you may be "doing it wrong"
 

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Discussion Starter · #9 ·
After the bike is warmed up it runs good. If I apply choke, idle decreases and I can smell its running rich. Full choke and it dies. Even cold, choke makes it too rich.

Yes bike was running good before exhaust hole saw mod. Idle and at throttle. Afterwards, not so well. After rejetting, runs good warmed up and at speed with no hesitation. Just idle horrible when cold and the pilot jets settings are so different from each carbs.

I like the exhaust sound but now I can not get my bike to idle good at startup and some intermitent missing.
 

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After the bike is warmed up it runs good. If I apply choke, idle decreases and I can smell its running rich. Full choke and it dies. Even cold, choke makes it too rich.

Yes bike was running good before exhaust hole saw mod. Idle and at throttle. Afterwards, not so well. After rejetting, runs good warmed up and at speed with no hesitation. Just idle horrible when cold and the pilot jets settings are so different from each carbs.

I like the exhaust sound but now I can not get my bike to idle good at startup and some intermitent missing.
I would have just went up one size on the pilot jets, to a 42.
but it may be possible you got the wrong jet. where did you get them?
I dont think the sizes are stamp on them.
and as preciously stated, do you know where the sync screw is, in between the carbs?
 

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Discussion Starter · #11 ·
Yes I do know where the sync screw is.

I got my slow jets from Honda dealer locally and they are stamped with the #45 on them. Also have new pilot screws, ring,spring, and washer.

Maybe I will clean them again.
 

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yes, I just took a look at my old pilots, and they are stamped.
I still think going up 2 sizes might be to much, is it the front or rear that has the light miss,
a little tweaking of the screw may be all you need to take care of that, are your plugs starting to foul out at idle?
 

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Discussion Starter · #13 ·
I went up to #45 instead of #42 slow jets because previous posts I found showed that going to #42's there was not any noticeable difference. I was out to 4.5 and 5 turns. After installing the jets, carb 1 was still at 4.5 turns to get that cylinder running best. Carb 2 is at 2.5 and runs good at that setting. The plugs look good with a white/grey on the tips.

With the pilots at such different settings, I just went ahead and yanked my carbs off again. Third time cleaning might be the charm. I am going to get a new can of carb cleaner too soak them in since my current one may have contaminate particles in it. I'll let you know how it comes out after another cleaning and sync.
 

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I'm coming in a little late on this thread but had similar problems. When I bought the bike it had a bit of rear-cylinder popping on decel and at idle, even after turning the a/f screw out 4.5 turns. I decided to clean the carbs and up my slow jet sizes. #40 slow jets were exchanged for a #45 for the rear cyl and a #42 for the front. Also up'd my main jets from #118 to #120 because PO put custom pipes on and didn't rejet and I figured why not just see what happens. Also put in new float seats and needles. Put her back together, tried sync'ing but my levels were drifting all over the place. I pulled off the rubber boots and rubbed in some silicone grease and let the silicone sink in for a few days. (If you search around there's some information on the voodoo of re-softening old rubber) At the time of the attempted sync'ing I also noticed I was still backfiring on my rear cylinder with 4.5 turns out, even with the new #45 slow jet. After a little confusion and thought, I realized I hadn't checked my float levels when I put the carbs back together. Sure enough the new float seats and needles pushed the floats 3mm too high. Put everything back together and tried sync'ing again, this time with much better results. Levels would only drift/bounce about 1 inch now and I could finally get my bike to stop backfiring at 3.5 turns out. I still feel like a #45 slow jet shouldn't need 3.5 turns out but it works so I'm sticking with it for now.

So as for the enricher... my enricher still works as it should. I need about 2/3 enricher to start her up in the morning and she hits about 2000 rpm after 2-3 minutes. I can put on full enricher and get 3000-3500 rpms. So in light of my experience (which isn't saying much) if you're getting a decrease in rpm with your enricher then I would think you over jetted or your sync isn't as good as it needs to be, ie vacuum leaks somewhere (most likely the boots). Well I guess the a/f screws/holes could be dirty or something like that. I've found that carbs are not difficult or complicated, just mysterious. Clean once and they don't work, clean them twice and they don't work, clean them three times and they work great.

This post got way too long.
Good luck.
 

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I'm coming in a little late on this thread but had similar problems. When I bought the bike it had a bit of rear-cylinder popping on decel and at idle, even after turning the a/f screw out 4.5 turns. I decided to clean the carbs and up my slow jet sizes. #40 slow jets were exchanged for a #45 for the rear cyl and a #42 for the front. Also up'd my main jets from #118 to #120 because PO put custom pipes on and didn't rejet and I figured why not just see what happens. Also put in new float seats and needles. Put her back together, tried sync'ing but my levels were drifting all over the place. I pulled off the rubber boots and rubbed in some silicone grease and let the silicone sink in for a few days. (If you search around there's some information on the voodoo of re-softening old rubber) At the time of the attempted sync'ing I also noticed I was still backfiring on my rear cylinder with 4.5 turns out, even with the new #45 slow jet. After a little confusion and thought, I realized I hadn't checked my float levels when I put the carbs back together. Sure enough the new float seats and needles pushed the floats 3mm too high. Put everything back together and tried sync'ing again, this time with much better results. Levels would only drift/bounce about 1 inch now and I could finally get my bike to stop backfiring at 3.5 turns out. I still feel like a #45 slow jet shouldn't need 3.5 turns out but it works so I'm sticking with it for now.

So as for the enricher... my enricher still works as it should. I need about 2/3 enricher to start her up in the morning and she hits about 2000 rpm after 2-3 minutes. I can put on full enricher and get 3000-3500 rpms. So in light of my experience (which isn't saying much) if you're getting a decrease in rpm with your enricher then I would think you over jetted or your sync isn't as good as it needs to be, ie vacuum leaks somewhere (most likely the boots). Well I guess the a/f screws/holes could be dirty or something like that. I've found that carbs are not difficult or complicated, just mysterious. Clean once and they don't work, clean them twice and they don't work, clean them three times and they work great.

This post got way too long.
Good luck.
Nice reply, and I too use a tiny bit of silicone grease around the boot.
float level is something I have not had a problem with, so there for it did not come to mind, and was not mentioned in the rebuild. but great idea to check them.
 

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Discussion Starter · #16 ·
Thanks for the reply. Very good info there. I'll check float level. Have not done that yet. I Wii check on how to soften hard rubber boots. I can get new from local Honda shop for $20 each. That's rediculous but these I have are not that bad but are somewhat hard. Carbs are still soaking. Not sure how long to soak them.
 

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what size main jets do you have in there?, 45's are huge for pilot jets on that bike, I have basically open exhaust, and a heavily modded intake, and many other mods on my 83 750 and Im only running 42 pilot & 120 main jets, my screws are both out 3.5 turns, and it Idles smooth.
 

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Discussion Starter · #18 ·
My main jets are 120. Only mod on my bike is I hole sawed thru both mufflers clear thru to the header pipe. I have read the bike is lean from the factory and that others have experienced no difference between a 40 and 42 jet. Jets are cheap enough. I could get some 42's and put in there.

I just want it right this time. I am tired of messing with the Carbs.

Should I go back to my size 40? Get size 42? Stay with the 45's?

I am wondering, last time I soaked the carbs, I used old somewhat dirty cleaner. Maybe I did more damage than good. New cleaner this time.
 

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I would check your float levels first. They should be at 7mm. If they are higher than 8mm that means not enough gas was in your bowl. The jets sit down in the bowl of gas so the more gas you have in the bowl, the more gas can get sucked through the jet. (just in case you didn't know, not trying to sound condescending) So if your floats are way too high, I would reset the levels and put the #40s back in. If your floats are lower than 6mm, than too much gas is in the bowl. I would reset the levels and leave in the #45s. If your floats are within 6-8mm then I would consider going down to #42s because it sounds like you're definitely flooding the carb.

Oh, that brings up another question. It is also possible the float needles are damaged or aren't seated properly etc. and this would allow too much gas into your bowl, despite your float levels. I've heard other people have problems with flooding which turned out to be from bad needles or fuel pumps at too high a pressure.

Also just to re-iterate, your carbs need to be at least close to sync'd before trying to diagnose anything air/fuel mixture related.

matt
 

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Discussion Starter · #20 ·
Wow! Great info. I am still working on the carbs. Being very Anal this time. Carbs look cleaner than I have had them so far. I am not real sure how to measure float height but will search here and be sure its right. Thanks for the help everyone.
 
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