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650 rejet size

  • Thread starter Thread starter Steamroller
  • Start date Start date
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Steamroller

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I am going to put some pod fliters and a pair of emgo shortys on my '83 650. I have searched but I haven't found a hard fast answer as to what jet sizes I will need to switch to. I don't really like the idea of a dynojet kit. I would like to just purchase the jets/needles that I need from z1enterprises. I know there can be multiple answers as to what size jets I should try, I would be willing to buy miltiple sizes of jets to try different combinations if someone would throw some numbers at me.
 
With Emgos it doesn't matter, it will run like crap anyway. They don't really filter much either.
 
+2 sizes for the pods.

up an extra +2 for the pipes (but you'll probably be okay with no extra increase over the +2 you need for the pods)

That gives you lots of room to bracket the jetting. Prepare for lots of plug chops and jet changes.

What don't you like about the Dynajets?
 
tkent02 said:
With Emgos it doesn't matter, it will run like crap anyway. They don't really filter much either.
Click to expand...

I know the emgos are packed like crap so I was going to repack them before I put them on. Feel free to recommend similar style alternatives.
 
BigD_83 said:
+2 sizes for the pods.

up an extra +2 for the pipes (but you'll probably be okay with no extra increase over the +2 you need for the pods)

That gives you lots of room to bracket the jetting. Prepare for lots of plug chops and jet changes.

What don't you like about the Dynajets?
Click to expand...

To clarify, are you suggesting a total +4 increase in main jet size and a +4 increase in pilot jet size?
For example, say I have 110 mains and 42.5 pilot jets. Are you saying I would need 110+(4*2.5)=120 main jets and 42.5+(4*2.5)=52.5 pilot jets?

What do you mean by "bracket the jetting?"

The dynojet kits come with:

Dynojet Kit Fits Suzuki 1981-82 GS650 Kit includes (4) 160 Main Jets, (4) 155 Main Jets, (4) Fuel Needles, (4) Main Air Correctors, (4) Adjusting Washers, (4) E-Clips, (1) Slide Drill, (1) Glue, (1) Installation Tool, (1) Plug Drill, (1) Screw

Do I really need all of that? I don't even know what I would need to do with the glue, drill bits, and screw. I figure it would just be easier and cheaper to purchase just the jets that I need. Would I need to change anything besides just the pilot jets and main jets such as needles?
 
Steamroller said:
To clarify, are you suggesting a total +4 increase in main jet size and a +4 increase in pilot jet size?
For example, say I have 110 mains and 42.5 pilot jets. Are you saying I would need 110+(4*2.5)=120 main jets and 42.5+(4*2.5)=52.5 pilot jets?

What do you mean by "bracket the jetting?"

The dynojet kits come with:

Dynojet Kit Fits Suzuki 1981-82 GS650 Kit includes (4) 160 Main Jets, (4) 155 Main Jets, (4) Fuel Needles, (4) Main Air Correctors, (4) Adjusting Washers, (4) E-Clips, (1) Slide Drill, (1) Glue, (1) Installation Tool, (1) Plug Drill, (1) Screw

Do I really need all of that? I don't even know what I would need to do with the glue, drill bits, and screw. I figure it would just be easier and cheaper to purchase just the jets that I need. Would I need to change anything besides just the pilot jets and main jets such as needles?
Click to expand...
With pods and non-stock pipes, figure 4-8 sizes on the main jets. Pilot jets can remain stock, but might need the mixture screws turned out a bit. You will need new needles.

Good luck buying new needles from Z1 or anywhere but DynoJet. THEY are what makes the kit worth the money.

Just for reference: DJ 160 mains are about the same as Mikuni 150, DJ 155 is about the same as Mikuni 145, but I was not aware that DJ jets came in sizes with odd numbers. I have only seen them with even numbers and an increment of two. :-k

Even the smaller main jet is up 14 sizes, are you sure that's the right kit?

You may not know what to do with those extra parts and the glue, but when you get the kit, complete instructions are included.

Good luck with your new adventures in carb tuning. Hope it runs better for you, and is worth all the effort and time you are going to have to put into it. :D

.
 
Steve gave a very comprehensive answer to the jetting issue and I don't have much to add to his answer.

I meant bracketing like in exposures in photography. A couple of main jet sizes either side of your best guess at perfect, so you have room to dial it in. I think you will be okay without changing the pilot air jets.
 
Hi there mate, I've been the pods and exhaust route and tuned it well both with a GS850 and a GSX-1100EF.

I'd recommend starting out around 15% over stock. So if, for example, you're running a Mikuni 100 size mainjet then you will want a 115 mainjet. Order the next size up as well, so in this example a 117.5 in addition to the 115.

You will most likely not need the pilot air jets but perhaps order a size *down* while you are at it, if they have them at the same place you're ordering mains. I had this work wonders for the lowend on my GSX1100EF.

Chain mainjets, up your needles two notches and reset your idle and airscrews then see how she goes. That's all it took to get my GS850 pretty close with pods and 4-1 exhaust, bar some minor fettling later on, and ran very well all the way through the range.

Cheers - boingk
 
Steamroller, although I did not see any mention of it, the assumption has been made that you are using Emgo pods. Is this correct?
 
koolaid_kid- I don't have any pod filters picked out at the moment. I could get K&N's or any other kind, doesn't really matter to me.

boingk- I appreciate the straight forward reply. I may just give your method a shot.

Does anyone have anything to add to boingk's method?
 
Steamroller said:
koolaid_kid- I don't have any pod filters picked out at the moment. I could get K&N's or any other kind, doesn't really matter to me.

boingk- I appreciate the straight forward reply. I may just give your method a shot.

Does anyone have anything to add to boingk's method?
Click to expand...

http://ape-store.com/shopsite/page25.html

I recommend the APE super pro air filters. Very similar to the K&Ns, but a hell of a lot cheaper. They look good to boot as well and fit perfectly into the 650 frame (well, I have an 82 650G so it may be a bit different) like they were made for it.

Also, I have 145 Racing Dynamic Jets in my carbs as we speak and it obviously ran on those before (Pods, and a Yoshi 4-1 pipe). However, I have not been able to fire it and keep it running for a test ride to see if it is correct.
 
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I'll throw out a number or two. 120-125 main jet.
I believe stock is 112.5. So, Up two sizes for pods. Up at least one for the pipes.
My current bike is my first Suzuki and I haven't "tuned" it yet. But, I have had several '70's Honda fours and this has worked for me in the past.
 
On most stock 650's main is 110 (mikuni scheme); the beauty of the dynojet kit is the needles- designed to work with the dynojet mains. I'm sure it's possible to work around them (and use stock needles) but it could be time consuming to get it to run right in midrange- where I seem to linger!
 
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