Need some Jet Suggestions!?

[tucker8541]

I have a 77' GS750, I am going to Air Pod Filters and straight exhaust (No Baffles). What do you guys recommend I go on the jets? Thanks Guys!

 

[Steve]

Have you done any searching?

I ask because this topic comes up rather regularly, so there should be PLENTY of answers.

However, the general recommendation is to go up 1 to 4 sizes for an exhaust change, based on restriction, and 3 to 5 sizes for pods, depending on quality of the pods.

.

 

[whiterabbitt]

let me suggest that you add some home made baffles to those cut cans, most retailers like dennis kirk sell diy baffle tubes from la choppers for fairly cheap and some 2 1/2 inch washers from hardware store to cap the ends. wrap fiberglass packing or steel wool around the baffle tubes, it helps.

I only suggest this because I cut mine the same as yours and found that you lose a ton of low end power and it is terribly annoyingly loud and the sonic vibration is grating. my suggestions come from personal experience. of course if you still have the original tubes in there disregard me. mine fell out thus necessitating the cutting.

good lookin bike btw and good luck!

 

[Pendulum]

Good looking cafe! I agree on the exhaust recommendations. My stock mufflers were both really damaged so I cut them off, and it's way too loud.

As for jetting, I went up 5 sizes on the mains for my GS550 for straight pipes and pod filters. I think it's still a wee bit lean, especially on the pilot circuit. I'll find out when I take her for a test ride on Sunday.

 

[1_v8_merc]

I went up 2 sizes with a Glasspack welded on, and it wasn't enough.

 

[TheCafeKid]

You can't just change jets. You need to move the needle clips as well...

 

[verde]

Hey tucker8541, I have 2 750 8 valves with basically that set-up. The header's-only one definitely lacks bottom end and is too obnoxious even for me. Definitely heed the advice of other regarding baffles of some sort. That said though my other one has funky long narrow straight pipes built off the stock 4 -> 2 that give a beautiful feeling power band.

Both are running no pods, just filter element to keep the bugs and leaves out, but jet similarly to pods. Off the top of my head I'm not sure where the mains ended up... probably 125s or 130s in the headers only bike and 120s or 125s in the other. Both bikes have 17.5 pilots. Needles on the 4th notch in both cases I *think* -- definitely the needles in the bike with the long pipes are set there. I will be running an AFR meter when I get enough spare time and see just how well my seat of the pants and plug chops worked. The headers only situation will be re-worked as well.

 

[whiterabbitt]

oh yeah I am currently running 110 mains with stock airbox and k&n filter. needle up one position and pilots right around 1 turn out. not perfect yet, but not detrimental to the engine either. still a bit rich down low

 

[tucker8541]

Thanks for all the recommendations, now looking into making some kind of baffle. I may of forgot to add that the exhaust is a 4 into 2, going straight exhaust too loud even for that? I really can't believe that the bike would be to loud! I kinda really like the idea of ****ing everyone off and scaring little children (Just me), just don't want to be pulled over every 5 miles.

 

[whiterabbitt]

its not just the volume, the sonic vibrations WILL bother you(experience speaking). kinda like holding onto an old push mower all day, except you add your feet, legs and rear.

the volume and tone might bother you, and will pi$$ off everyone else until your riding at a good speed, like 50+mph, where you kinda outpace the soundwave and are gone before anyone gets too annoyed

the real kicker is the power loss. and difficulty getting it tuned.

 

[tucker8541]

Anyone have any pic's of their exhaust Baffles they made? Just need an idea where to start. Also, if you have the exhaust baffles you guys went with. Thanks again.

 

[verde]

I kinda really like the idea of ****ing everyone off and scaring little children (Just me)

:-s I'm not completely against a little bit of noise, but this thought process is all wrong. I really hope you're just joking here. A custom bike should sound different because you built it yourself, not because you want to ruin other peoples' day to somehow bolster yourself up in your own head.

Anyone have any pic's of their exhaust Baffles they made? Just need an idea where to start. Also, if you have the exhaust baffles you guys went with. Thanks again.

Google image search "exhaust baffle" for more inspiration. You can have flow through or force the exhaust gas to navigate its way through a different path. With or without packing. If you use steel wool packing instead of glass pack, use stainless steel wool as the regular steel wool will rust away fairly quickly in that environment. You probably have to order that online(mcmastercarr likely has some). I have some ss scotch bright scoring pads I intend to try for a weed eater motor powered project, but they are made of fairly thin ribbons so we'll have to wait and see how long that holds up.

Here's a thread with some mini copper baffle designs:
http://www.dotheton.com/forum/index.php?topic=11248.0

Numerous retailers carry these style "universal" baffles:

This guy cut slits perpendicular to the tube and dented one side in:

Spiral style baffles that were discussed in the same street rod thread as the baffles above:

 

[whiterabbitt]

the ones I made are similar to the ones in the do the ton forum posted earlier, I recommend 1 inch tubing for the baffles. sounds and feels better than the set I made with 1 1/2 inch exhaust tubing. you will need a couple 1 1/2in. id to 1in reducers and a couple of 2 1/2 in od, 1in id washers or whatever best fits the ends of your megs.
mine are press fit but that was my choice so i could easily change anything I wanted.

 

[james R Parker MDa]

Cool picks always loved painten Indians bikes s r

 

[james R Parker MDa]

exsactly what love is about

exsactly what love is about

who didn't ride a 2 wheeler

 

[koolaid_kid]

Tucker, if you know someone with a wideband (a.k.a. snuffer) such as an LM-1 or LM-2 tuning is much easier, faster, and more accurate than using the plug chop method. And it only takes one set of plugs.
Just a thought, since you will need to tune all 3 sections of the carbs. Mains, needles and pilots. In that order, btw.

 

[tucker8541]

Thanks for the advice, working on them know. Looking into new ideas and style I like for the end of the exhaust. Fine tuning the carbs now.

Verde loosen up!

 

[whiterabbitt]

might want to get that exhaust in order first as that will change your tuning.

and kool-aid, the vm carbs are tuned bottom up not top down

 

[verde]

This is me loosened up Good luck with the tuning and keep us posted.