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I have a 2002 Honda Shadow ACE 750 with cobra straight pipes with no baffles, stock air filter, and I just upgraded added a stage 1 dyno jet kit and followed the directions on the box. When I started it back up it ran badly and popped when I decelerated at lower speeds. I ended up backing out both a/f mixture scews out to 4.5 turns out and the popping is manageable, but still very much present. It also starts kind of hard when it's cold. I didn't upgrade the pilot jets and I have no clue what size is in it. I also don't know what the stock size of the pilot jet is and what I need to move up to. Is upgrading my pilot jet going to fix my problem? HELP!!
 

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No, you don’t need to upgrade your pilots. Only if you’ve fully opened up the intake and exhaust as much as you possibly can should you touch the pilots, and even then some people say don’t touch em.

You are currently in the middle of figuring out your jetting, do you know what the size of any of the jets you put in or took out were? What needle position? Shims?

Carburetors don’t follow directions. The words will get you somewhere close to correct but with a carb the rest is feel and sound.
 

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Discussion Starter #3
Dj106 for front cylinder carb, and dj110 for rear cylinder carb. The e-clip is set on groove#2 from the top. The main Jets I pulled out were cheap and had no markings on them...
 

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You definitely do not need to change the pilots, I only changed from the stock 40 to a 42 when I went from 128 to 132 as my smallest main jet. You are nowhere close, your issue lies elsewhere.
 

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There is magic, luck and small sprinkling of science to help mix things up with jetting and like snowflakes every bike is different.
Testing is the real way to sort things out and taking the carbs on and off a 750 ACE is a slow process, it does get faster with practice though.

@Froth is right you have to work out your main jetting first and then the needle height.
I think the quoted DJ mains should be close for a stock intake.

The pipes with no baffles are really messing up the balance of the tune and costing you bottom end and mid-range power and really that is where the 750 ACE is strongest, it is a fairly low speed engine and there is no top end to take advantage of the free flowing pipes.

With the open pipes, I'd actually try dropping the needle 1 groove and putting the clips in the highest spot, it sounds counter intuitive, but I think it may help due to the crappy flow velocity with the exhaust. Testing will tell.
Normally I'd agree with Froth on the Pilot Jet, but in this case I would give 42 jets a try, at 4.5 turns out on the idle mixture screws you are well beyond doing any good and they are going to fall out on the pavement somewhere. Some people may suggest a 45 slow jet, don't bother, if it needs that there are more problems that is attempting to cover.

One thing I'd try since you have had the carbs off is to check the intake boots/insulators for leaks between the carbs and the heads.
If they are leaking you will just be chasing your tail with the jetting.
Do this outside, don't breath the fumes.
With the bike idling spray aerosol carb cleaner around the joints of the carb boots, if the idle changes speed you have a leak.
In a second or two you should smell as the cleaner comes out the exhaust, don't breath it in.

Also check all the stock air cleaner boots and hoses are in place with no gaps or cracks.

Seriously consider putting some kind of baffle in the pipes, even cheap, short can opener style ones should help point you in the right direction and not quiet it down a whole lot if that is your thing.
There are YouTubes to watch on the problems tuning drag pipes for street use, that may not be specific to your bike, but will give you an idea of the dilemma they present.

Good luck and let us know how you get along.
 

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Discussion Starter #6
Thanks! Since I'm stuck at the house all week I'll be tinkering with it. Starting with the easy stuff first.
 

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Without knowing what pilots are in it(stock would be 40 most likely) and with a complete stock intake and no timing advance I would be seriously surprised if a 42 Pilot jet ran well with everything properly connected, However I’ve been wrong before! Reality is these engine have all kinds of weird quirks, I’ve seen some crazy oem jetting inside these carbs and they ran great, somehow.
 

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I'm hoping the carburetor is clean, I have seen people try to rejet and then wonder what is wrong with clogged up messes.

@Froth usually we are not too far apart on this stuff although we get there sometimes in different ways. (-;
My thinking on this is the Stage 1 DJ kit works OK with a stock intake and tuned aftermarket exhaust.
This is far from a tuned exhaust and is effectively going to be close to 1 7/8" ID straight pipes as opposed to the 1 1/4" stock pipes and is probably going to benefit from going leaner in the mid-range, hence the lower (thin DJ) needle and at the lower end it will need the richness restored. While it also runs against my grain using the pilot jet to do this with an engine running the stock filter setup and no greater air capacity, it does seem to be the easiest way to accomplish it.

That's where my head is at on this one.

The easiest fix is probably to return the Cobra pipes to the original condition with the baffles with this jet kit installed as per the DJ instructions and a stock 40 Pilot Jet.
There have been I don't know how many thousand 750 ACE bikes run successfully that way and it is probably worth a one or two horsepower increase over a stock as supplied 750 ACE.
Sure they are going to "pop corn" on the over run to a certain extent no matter what you do, but that is really the nature of the beast and I think largely related to the intake and exhaust timing.
 

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Groove 2 sounds too low to me, usually it's groove 3-4. But when it is said in the manual it should be ok I think. csroad is right, no baffle (and stock air filter ?!) at all makes it difficult for sure!

As far as I know, the Dynojet sets are pretty spot on in most cases. When not running with throttle she is either too lean or too rich. Too rich: giving throttle (mid range) she's dying it's too rich.
It's also not easy to get completely rid off of the backfiring, and to a certain extent it does no harm at all. And normally, a different pilot jet is not necessary, referring to DJ, due to the tapered needle. But I made the experience that a bigger pilot jet can help. Turning them our like 4+ you need a bigger pilot.
What sounds a bit strange to me is the combination of stock air filter and exhaust w/o baffles. Maybe the balance is missing, when you have free flow on the one side u need it on the other side as well.

You also should check the floating level as well, when this is messed up she's either too lean or too rich. Check with brake cleaner or starter spray if there is an air leak, I had that problem...

Did you clean the carb?
 

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Discussion Starter #10
When I
Groove 2 sounds too low to me, usually it's groove 3-4. But when it is said in the manual it should be ok I think. csroad is right, no baffle (and stock air filter ?!) at all makes it difficult for sure!

As far as I know, the Dynojet sets are pretty spot on in most cases. When not running with throttle she is either too lean or too rich. Too rich: giving throttle (mid range) she's dying it's too rich.
It's also not easy to get completely rid off of the backfiring, and to a certain extent it does no harm at all. And normally, a different pilot jet is not necessary, referring to DJ, due to the tapered needle. But I made the experience that a bigger pilot jet can help. Turning them our like 4+ you need a bigger pilot.
What sounds a bit strange to me is the combination of stock air filter and exhaust w/o baffles. Maybe the balance is missing, when you have free flow on the one side u need it on the other side as well.

You also should check the floating level as well, when this is messed up she's either too lean or too rich. Check with brake cleaner or starter spray if there is an air leak, I had that problem...

Did you clean the carb?
When I did the DJ install I also cleaned and rebuilt the carb. Whoever had it before me did a crummy job because I had a tiny fuel leak from a cheap seal. I also have a K&N air filter sitting at home. I'll probably put that in and see what happens next.
 

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ok good! I just did the rejetting myself (and had not much clue in the beginning...) and you have to know, that sooner or later you will hit the sweet spot. It t may take some time to find the right setup, but you learn about carbs and the bike.
 

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Discussion Starter #12
Well I may have found the culprit. I sprayed carb cleaner on the carb boots and the motor started hesitating when I sprayed the front one. Not sure if it's a bad boot or if I didn't put it on all the way:unsure:
 
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