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V&H megaphone jetting

trevor

trevor

Forum Guru
Past Site Supporter
Just ordered V&H megaphone for my 1980 gs750e can someone tell me what jetting kit I will need?
Thanks,
Trevor
 
Jetting guru's can chime in but a Dyno-jet stage one kit is probaly what you need.
 
DJ says you can use either stage 1 or 3 with your set-up. If you change the intake side to anything more free-flowing than stock you'll have to go with stage 3 or you'll be too lean.

http://www.dynojet.com/pdf/3130.pdf

Or you can search the GS database for the jet chart and order what you need. You can't go wrong with the DJ kit though. It's complete with new needles, and really good support from what I hear.

Happy jetting!
 
I'd suggest the Dynojet kit, too. You will still have to fine-tune it with some plug chops, but it will get you there faster and easier
 
So I got the pipes on and with some carb adjustment it seems to be running great. No flat spots. I have not put in a jet kit as of yet. I have been monitering the plugs and they all look really good (dark not lean) except plug #2 it is pretty white. I have backed the carb screws off and readjusted so that they are all the same adjustment. Number 2 carb screw was a little leaner setting. So went out for a test ride and the #2 plug still is white. Anyone have any thoughts? I'm pretty new at this and had the help of fellow GSr AZR.
Thanks
 
Get that Dynojet kit. It's important to not run the bike lean because that means hot.

hot = bad (for air cooled motorcycles)
 
Don't mean to be jumping in the thread here but being I have no experience jetting for 4 into 1 pipes I've got some questions I'm dying to get figured out. Before Trevor put the 4 into 1 on I looked at his plugs and they were all lean, not a spec of brown/black or carbon...but the bike ran great, no hanging, flat spots, etc.. Stock pipes with a K&N filter. He put the new Vance pipe on and immediately 3 plugs changed colour. # four looked great, nice brown, the other two a bit more to the lean side but still not a bad brown and then #2 is as lean as lean can get and hot, the electrode is showing signs of being too hot. So here lies my confusion. With the first plug colours I couldn't figure out why they were looking lean yet the bike ran great. With the plugs after the new pipe was put on I was expecting to see all the plugs looking like #2, lean colours and signs of being too hot...but 3 out of 4 are not. Now Trevor hasn't pulled apart the carbs so there is no telling what jets are in there of course and I know that could be the answer to all of this but any ideas to cure me of these questions rolling around aimlessly in my head would be greatly appreciated.
 
trevor said:
... I have backed the carb screws off and readjusted so that they are all the same adjustment. Number 2 carb screw was a little leaner setting.
Click to expand...
What "carb screws" did you turn? Which way? How far?

I ask, because the only external adjustment on your carbs is the "IDLE MIXTURE ADJUSTMENT SCREW", which is pictured below:
IMG_2958.jpg


Turning them out to the same number of turns is only to get them to a starting point from which you will do some fine-tuning. Most of us recommend starting with three full turns to make sure your mixture is rich enough to start and run properly, then, when the bike is fully warmed up, slowly turn each screw in, listening for the point where the engine either runs the fastest (it won't be much of a change) or starts to decrease. If you get to the point where it decreases, back the screw out about 1/8 to 1/4 turn and go to the next carb. Due to differences in the tolerances of individual parts in the carbs, there can easily be 1/4 turn difference from one carb to another.

By the way, turning the screws OUT (anti-clockwise) will richen the mixture, turning them IN (clockwise) will lean it, and this is for the IDLE mixture ONLY. That circuit in the carb is only good to about 1/4 throttle, so it is responsible for most of the low-throttle operation, too.

If you have only done your testing at low-throttle settings, it will not be obvious that you need to change your jetting. It is your MAIN jets that need to be changed, they don't even get used until over half-throttle. If you do some 3/4 to full-throttle runs with your stock jets, you can probably plan on replacing pistons and cylinders, too. :eek:

.
 
#2 supplies vacuum to petcock, maybe a leak drawing air in. Are carbs clean, could be something clogged also.
 
paco13 said:
#2 supplies vacuum to petcock, maybe a leak drawing air in. Are carbs clean, could be something clogged also.
Click to expand...
I ordered the stage 1 yesterday from Z1 enterprises so with help from AZR I'm going to have a look at what I've got going on in my carbs later today and have it ready to install the kit. Also got progressive rear shocks showing up today.
Boy it sure is easy to spend money!!:o
To everyone who has responded thanks very much and I will keep you posted on how she is running.:)
 
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