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Fixed bogging at hwy speed

6K views 10 replies 10 participants last post by  CSRoad 
#1 ·
I have a 01 hondow shadow 750 spirit with vance&hines pipes and k&n filter I bought it about a month ago it was cutting out top end and running bad at hwy speed I bought a jet kit had 3 stages I put stage 2 112 main jet front and 115 rear and put a shim in needle ran better top end but worse at hwy speed. So off comes carbs went stage 3 115 front 118 rear took out shims and moved clip too slot 2 wich put the needle down further put it back together it is a new bike pulls all threw rpm range and crisp and clean at hyw speed WOW IT RUNS AWESOME just wanted everyone to know
 
#3 ·
Thanks for sharing your fix, it may help a lot of others get in the ballpark when they have carb problems.
 
#8 ·
Hello. I'm new and got an 2002 Shadow spirit vt750dc running after someone let it sit for two years. Rebuilt the carb and changed out a loundry list of stuff including the petcock, fuel pump etc. I got a stage 3 jet kit and put them in since the old ones were just bad and fouled up. Changed the float needles out too. Everything looks new and clean. It runs and seems fine at first but then when barely open the throttle past say 1/4 the way it starts too bog down like what hours did. I top out at maybe 50mph. The description for the jet kit says its a #112 and 115. It came with two washers for each air needle. I dont know if these jets are causing thbe problem. I put one of the pointy air filter mods on. I also tried riding it with the intake removed and just the air intake necks and same thing. I adjusted the air/fuel and idle to specified settings and tried tweaking it. No dice. I'm going to put thbe original airbox back on once I get a filter and see if that helps. I figured the bigger jets would need a better air intake. However I just can't get it right. Any help would be appreciated. I have also replaced the fuel filter, fuel lines as well. Not sure of what else to adjust. Has new plugs and wires. I ordered some of the OEM jets and if nothing else, will go back to stock everything. Just don't want to pull the carb again but I'm at the end of the line here. Below is the link to the Amazon part I bought. Maybe soomeone knows enough to tell me something I don't know. Thanks in advance.

https://www.amazon.com/gp/aw/d/B00HT8C8C4/ref=yo_ii_img?ie=UTF8&psc=1
 
#9 ·
When you changed the jets, did you also change the exhaust? If not, you can only push so much through the stock exhaust system. If not you got the cart in front of the horse. Open the exhaust first, THEN push more air/fuel through it.
 
#10 ·
Carb tuning can be a bear sometimes. But when it's right, it's well worth it. It's hard to keep that in mind when you're pulling the carbs for the THIRD, FOURTH time, but it'll be worth it.

A little more information would help us keyboard engineers help you sort out the issue.

How does it ride at a steady cruise speed?

How does it start when cold (does it NEED choke or else it pops and farts?)

Does it need choke until it is good and warm?

How does it react in 2nd/3rd gear at WOT?

How many turns are the idle screws now?

Some thoughts:

To help you decide if it needs MORE or LESS fuel, you can try removing the filter entirely (for a short run) and also try restricting airflow by covering part of the opening. If it runs better with more air (no air filter) then the jets are rich. If it's the other way, then you're running lean.

There is also what is called a slow jet. This jet handles fuel flow right off idle and up to about 30% throttle. The main jets aren't opened up much before that. Many folks will adjust the idle screws to try and rid themselves of a "just off idle" lean condition, but really, the slow jet is the culprit. What happens is that they over richen the idle screw, which DOES help overcome the slow jet's issue, but then idle is way rich.

Also, as Smilie said, if you didn't swap out the exhaust, the larger gets are likely still the bottleneck. if it can't get out, you're not gonna get more in. What exhaust is on the bike? Stock/V&H/ any baffles? Inquiring minds want to know. :grin2:

Here is a thread that I started a while ago that may help:
http://www.hondashadow.net/forum/72-technical-discussion/360994-beyond-k-n.html
 
#11 · (Edited)
It is my belief that the stock exhaust gets a lot of bad comments, but is well designed, promotes good exhaust velocity and is quiet.
With a stock engine, changing it out will give you a horsepower or so if jetted to suit and a better sounding bike that might wake the neighbors baby.
IMHO it is not a real bottleneck on the VT750's from this millenium until you do more modifying to the engine, a properly tuned spike intake setup might push that point.



That so called "Stage 3" kit is way too lean for a spike air filter/intake, typical starting point for those are main jets in the mid to high 130's and 42 pilot jets, that should get a somewhat rideable bike to start with.
On the other hand with those "Stage 3" jets and raised needle it is probably a little rich for the stock ham can filter box.


Keep an eye on the spark plug color as you tune things, it is a window to the soul, there is a lot of info in these forums on doing plug cuts to get the bike running right at each point in the operation, but get the main jets diated in at wide open throttle first.


If you want to reduce your work get FactoryPro.com to make you a carb kit to suit with a few alternate jets, it costs more, but that cheap "Stage 3" kit wasn't so cheap after all was it?
 
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