Rejet Honda Shadow Spirit 750 and is not running right - Honda Shadow Forums : Shadow Motorcycle Forum

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Old 10-14-2007, 05:34 PM   #1 (permalink)
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Default Rejet Honda Shadow Spirit 750 and is not running right

I have a 05 Honda shadow spirit 750, and put Vance and Hines straight shots exhaust on(with the baffels in), then took it to the local Honda dealership to have the carbs rejetted (with a dynojet kit, stage 1) and a k&n filter.

My question is that since I got it back it seems that it has a lot less power when going up hills, and also the exhaust is poping alot and it seems like it gets worse as time goes on. Is this normal loss of torque from the pipes? Also my gas milage went from 65mpg down to 45mpg. Did they not jet it right, or is this normal???
Thanks, Brandon
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Old 10-14-2007, 09:33 PM   #2 (permalink)
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Default Re: Rejet Honda Shadow Spirit 750 and is not running right

Quote:
Originally Posted by bvette85
I have a 05 Honda shadow spirit 750, and put Vance and Hines straight shots exhaust on(with the baffels in), then took it to the local Honda dealership to have the carbs rejetted (with a dynojet kit, stage 1) and a k&n filter.

My question is that since I got it back it seems that it has a lot less power when going up hills, and also the exhaust is poping alot and it seems like it gets worse as time goes on. Is this normal loss of torque from the pipes? Also my gas milage went from 65mpg down to 45mpg. Did they not jet it right, or is this normal???
Thanks, Brandon
Have a read into this posting:

http://www.hondashadow.net/forum/vie...723&highlight=

Let me confirm that I am not an expert on the topic and had a great deal of assistance from a few individuals, specifically Litnin of this forum.

I had a problem with a rejet on my bike, which was actually done by a motorcycle mechanic. I had similar issues with the second rejet attempt. The larger jets from the kit were installed, which in effect, reduced the torque and overall power. The engine consumed more gas as well. On the third and final rejet, the recommended jets were placed back in and the needles set up one notch from the recommended 2nd position to the 3rd clip. The bike has more power in all ranges of the throttle; at mid range, 25%-75% throttle, and at the high end, 75%-100% throttle.

Before the final rejet, I talked to the dynojet tech dept. They said to take the air filter out and run the bike as a test. I did that and the bike ran superbly. I called them back and they told me the bike needs to be leaned out. They suggested putting the smaller jets, 102 & 106, back in and set the needles at clip 1 as well as taking off the air injection assembly to eliminate the popping (I did not end up taking the air injection off). I followed Litnin's advice and replaced the larger jets with the smaller ones (102 & 106) and placed the needles at position 3, as the recommended 2nd clip position had the bike starving for fuel at a steady cruse speed as observed after the 1st rejet attempt.

Download the PDF dynojet kit instructions for your bike before talking to the mechanic to determine the recommended jet sizes and the needle clip position. Then state your concern to the mechanic. Assuming that he used a kit, which mine had 2 options for jet sizes, ask him what size jets were placed in the carbs, the needle clip position and if he drilled out the slide lift hole as the instructions specify.

If you get stuck, you might want to PM Litnin as he was very helpful to me. Let us know how this unfolds.

Hope this helps!
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Old 10-15-2007, 10:20 PM   #3 (permalink)
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Thanks...that helped me out a little. Im going too look at my dynojet instuctions to see what jets and rod position they say to use, as well as which ones the machanic did use(I had him write all of it down). I will try taking the air filter off and see how it runs.

I kept reading about loosing a little gas milage with a rejet/pipes/k&n airfilter but I lost about 20 miles per gallon....Is this normal???

I think they main problem is finding a machanic that gives a damn and just doesnt rush through it, to get it done! Thats why I try to do all that stuff myself but being my first bike I didnt want to just start tearing into the heart of the beast.
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Old 10-17-2007, 09:13 PM   #4 (permalink)
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I checked into it and my jet kit only has the main jets and needles...no pilot jets.
The jets used were 104 in the front main, and 106 in the rear main.
The needles were set to the 3rd grove from the top.
The mixture screws were set to 2 turns out in the front, and 2.5 turns out in the rear.
Does this sound right?
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Old 10-17-2007, 10:03 PM   #5 (permalink)
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Quote:
Originally Posted by bvette85
I checked into it and my jet kit only has the main jets and needles...no pilot jets.
The jets used were 104 in the front main, and 106 in the rear main.
The needles were set to the 3rd grove from the top.
The mixture screws were set to 2 turns out in the front, and 2.5 turns out in the rear.
Does this sound right?
According to the dynojet kit PDF #1182 ( http://www.dynojet.com/jetkits/motorcycle/honda.aspx ) for your bike and exhaust configuration, it suggests the DJ 102 jet for the front carb and the DJ 104 jet for the rear carb. The jets you have in there right now are too large. The performance conditions you are describing is indicative of over sized jets. I was in the exact same situation as you with my 2nd rejet attempt when the jets were too large. Again, I am not an expert, but I was recommended by Litnin, whom I respect greatly for his knowledge, to go with the smaller jets, in your case the 102 and 104.

Based on Litnin's experience in rejetting, he advocated adding one clip positon to the recommendations as stated in the installation kit. Your kit recommends the 3rd clip. Litnin's theory would suggest the 4th clip from the top, which in effect will provide more torque in the mid throttle positon and keep the bike from starving for fuel when at a steady rate (speed) cruising throttle position. I followed his recommendation and the performance of my bike was much better.

Unless you are going to an after market airbox, then you would might want to have a look at a larger pilot jet. For your set up, it is not recommended.

The PDF installation kit calls for the mixture screws to be set to 3 turns out. At 2 & 2.5 turns out the bike is running too lean in the idle position when decelerating which is going to make the bike pop - probably quite a bit. I have my screws turned out 3.5 turns - front and rear. There is still a bit of popping, but nothing to get too exited about. I've ordered a dyna-3000, which other users have said it reduced topping significantly or eliminated it. However, I am getting it as a performance enhancer, not necessarily to completely eliminate the popping which does not have any adverse effects on the engine.

I would suggest taking it back to the mechanic and get it done right. If you are still not sure, PM Litnin (go to search feature and search for author).

Hope this helps, bikervas
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Old 10-17-2007, 11:42 PM   #6 (permalink)
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Default Re: Rejet Honda Shadow Spirit 750 and is not running right

Quote:
Originally Posted by bvette85
I have a 05 Honda shadow spirit 750, and put Vance and Hines straight shots exhaust on(with the baffels in), then took it to the local Honda dealership to have the carbs rejetted (with a dynojet kit, stage 1) and a k&n filter.

My question is that since I got it back it seems that it has a lot less power when going up hills, and also the exhaust is poping alot and it seems like it gets worse as time goes on. Is this normal loss of torque from the pipes? Also my gas milage went from 65mpg down to 45mpg. Did they not jet it right, or is this normal???
Thanks, Brandon
bvette85,

It sounds like you are running way too rich on the main jets and too lean in the idle circuit.
That is why you are noticing such a drastic fuel mileage drop.
You are going to notice a little bit of a drop (probably 3-5mpg), that's
simply the price for power. However, 20mpg is way too excessive.
That is most likely because the main jet in that rear cylinder is way too big.

It's been my experience that when Dynojet says to use a given size
jet, they are usually right on the money. They only problem I've found is
that their recommendation for needle position has always been 1 notch off.
If Dynojet says it should be in position 3, I run them in position 4, from the top (more rich).

I looked at the Dynojet instructions for your bike and according to them,
you should be running a 102 in front and a 104 in the rear.

My suggestion would be to put the 102 in front and the 104 in the rear.
Run the needle in the 4th notch from the top.
Be sure that the mechanic drills out the slide lift holes in the vacuum pistons.
That hole HAS to be enlarged or else the calibration of the needles and
main jets will be off. There should have been a drill bit included in
the kit to drill that slide lift hole.

I have never had to change the pilot jets, when rejetting for a stage 1 kit.
At idle, there is very little change in the fuel demands and/or the air flow.
There is plenty of adjustment in the existing pilot jets to compensate for
the change. Dynojet recommends starting with the screws 3 turns out.
I'd start with that and if it needs more, give it 1/4 turn out at a time until
the popping stops. You should not have to go more that 3 1/2 turns.
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Old 10-18-2007, 03:44 PM   #7 (permalink)
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Great advice...I might try doing it myself this winter.
Another thing is when I asked the mechanic that worked on it if he synced the carbs he said that you dont have to with the shadow spirit 750's because they are connected...Is this correct? Or is he just an idiot?
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Old 10-18-2007, 10:50 PM   #8 (permalink)
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Quote:
My suggestion would be to put the 102 in front and the 104 in the rear.
Run the needle in the 4th notch from the top.
Be sure that the mechanic drills out the slide lift holes in the vacuum pistons.
That hole HAS to be enlarged or else the calibration of the needles and
main jets will be off. There should have been a drill bit included in
the kit to drill that slide lift hole.
My Instructions dont say anything about drilling out the slide lift holes. It did come with a 5/32 drill bit, but it says to use it to drill out fuel mixture screw plugs (the plugs cover the mixture screws so they stay set at factory settings)

Thanks litnin....from what I have heard, your the one to talk to...and I thank you for any help you give me!
And Bikervas...thanks for the help...It sounds like you have gone through what I am, and hopfully your advice will save me a little pain and give me more time to ride!
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Old 10-19-2007, 07:59 AM   #9 (permalink)
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Quote:
Originally Posted by bvette85
Another thing is when I asked the mechanic that worked on it if he synced the carbs he said that you dont have to with the shadow spirit 750's because they are connected...Is this correct? Or is he just an idiot?
Your mechanic doesn't know what he's doing.

When you run multiple carburetors, they HAVE to be connected together
or else when you give it throttle, only one is going to work.
That's WHY you sync them. They both will not flow the same amount of air,
generally, on initial assembly or when you change the air flow characteristics
(like changing pipes and a filter).
You have one base carburetor that is not adjustable. When you turn
the sync screw, you are adjusting the other carburetor to be as close as
possible to the base carburetor.

It amazes me how some people call themselves mechanics.

Quote:
Originally Posted by bvette85
My Instructions dont say anything about drilling out the slide lift holes. It did come with a 5/32 drill bit, but it says to use it to drill out fuel mixture screw plugs (the plugs cover the mixture screws so they stay set at factory settings)
Yep, you're right. Sorry about that. I went back and read the
instructions again and that kit doesn't require the slide lift hole to be enlarged.
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Old 10-19-2007, 10:38 AM   #10 (permalink)
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I had a similar problem with my 03 ace 750. I bought the bike, put a set of jardine turn out pipes on it and brought it in to have it rejetted. When i picked the bike up from the shop and rode it home it ran like crap and the milage was terriable. i was like 10 mpg off what i normally get and there was a ton of popping on decel. Well since i spent a ton of money already I figured the mechanic did something wrong so i sat down and pulled the carbs and what do you know he never rejetted it....just said he did. I was MAD as hell. Anyways a few phone calls later and a little ass chewing i had the mechanic at my house rejetting the carb while i watch. (kind of a old friend) using the dynojet kit stage 1 kit. which had 106 and 110 jets in it. He drilled out the slides and tweaked everything. Now the bike runs great and i only lost 4-5 mpg. If i were you id make sure that the mechanic ACTUALLY put your kit in and not just adjusted the pilot screws so that it sounds good.

O and you dont have to change the pilot jets....just the main jets...the pilot circuit can be controlled by the mixture screws on the carbs. Ive heard of people using a stage 3 jet kit which is 138/134 jets with a k&n and vance and hines drag pipes and not have a problem....these bikes come VERY lean from the factory and you can go real big with the jets before you get to the rich side.

p.s. Make sure you have the slides drilled....MAJOR difference in how the carb performs with the jets.
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