Just came back from my first ride after "needle shim mod"

[David Bo]

Wow, I really felt the difference... I shimmed my needle earlier this weekend and turned my carb's bottom screw open about a half turn (after drilling out that little metal plug). I cut the airflow restricter off of my existing air filter and opened up the holes in my muffler a from 1/4" to about 3/8" to relieve some additional back pressure. It feels like these mods added "at least" a couple of ponies to the engine. I can't wait to install the new exhaust next weekend. I am also planing on installing a K&N filter to replace the cut-up factory one.

It is pretty cold in New England today so I only went about 8 miles before my face started to freeze. Thanks for all the "How to's" guys!!! :cool:

[Easy Rider]

I am also planing on installing a K&N filter to replace the cut-up factory one.


I didn't think there was a direct K&N replacement ???

Anyhow, be careful with that. If you REALLY open up the intake, you will probably need to re-jet too. Since you got through the needle shim, that wouldn't be much of a problem though.

You can see roughly what the K&N will be like by running briefly without an air filter at all.

[patrick_777]

If you shimmed, you should have also drilled out the mixture screw, right? You might can get away just richening up the fuel/air ratio without a filterbox on. That might get you where you need to be without jetting.

Might. I haven't done it, so others will definitely know better.

[music man]

[quote="David Bo":33jj7x5h] I am also planing on installing a K&N filter to replace the cut-up factory one.


I didn't think there was a direct K&N replacement ???
[/quote:33jj7x5h]


Yes there is, but it is listed for a Suzuki GS500, not the GZ. But it is a direct replacement, just like the Hi Flo brand that I have in my bike is.

[David Bo]

Thanks Easy... I was actually planning on replacing the jet too. I figure since I already did the other two carb mods, what the hell... I was surprised to see how easy it was to get to the jet. I actually have it in my hand as we speak. After reading the post entitled "rejetting part 1", I think I am going to purchase a #147.5 jet. Do you have an opinion on this?

[Easy Rider]

If you shimmed, you should have also drilled out the mixture screw, right?

That is an IDLE (low speed) mixture screw.

It has so little affect at med. and high speeds that the placebo effect doesn't even come into play !!! :biggrin:

[Easy Rider]

I think I am going to purchase a #147.5 jet. Do you have an opinion on this?

Not really. A wild guess would be not to go bigger than the European models.......but that might not be enough with no intake restriction. Don't know.

I would expect your gas mileage to go down a tad.
Isn't that what others have reported ??

[David Bo]

The K & B Filter Number I ordered was SU-5589. I'll let you know if it does not fit but I believe it will as it is the one for a GS500. Yes, I did drill out the metal cap for the idle screw. I drilled it about an 1/8" inward until I could see that tiny hole in the middle of the plug start to widen from my drill bit. Then I hooked the remaining portion of the plug with a little hook tool I have. A little yank and it popped right out. I was "overly" careful because I did not want to hit the actual adjustment screw with my drill bit.

So, I have read in other posts that the factory jet is most likely a #120 and the best replacement is a #147.5? Does anyone want to offer any advise before I drop 3 bucks on the wrong size replacement jet?

Thanks! David Bo

[David Bo]

OK... The Suzuki place did not have any of the correct jets for the GZ so yesterday I ordered a #140 and a #145 and they came in today. Having done the other carb mods this weekend, I was excited to see what going from a #120 jet to a #140 jet would feel like. All I can say is WOW!!! I purposely went for a ride where I could approach a steep hill at around 40 mph in five gear and then gun it... After 1/4 mile of up hill I was approaching 55 MPH!!! That is pretty good considering two weeks ago, I practically would have to downshift to forth going up that same hill. On a good day (last summer) the bike could only hold it's own at a steady 40 MPH in fifth gear...

Anyway, if anyone is considering doing the "three step carb modification", I would highly recommend it. Keep in mind that I already had drilled out my muffler and cut the in-take restricter out of my stock air filter. Next weekend (I hope) I plan on swapping the exhaust pipe with a JC Whitney extra long reverse megephone muffler and installing a K&N air filter (if they come in before then). At that point, I will most likely stick the #145 jet in the carburator too.

Fun, Fun, Fun !!! :2tup:

[Easy Rider]

Anyway, if anyone is considering doing the "three step carb modification", I would highly recommend it.

Ah, but the whole story isn't in yet. Will be interesting to see what your gas mileage does after all the changes are done. IIRC, the others who did it ended up in the low 60's ....down from the low 70's.

And for those who are not mechanically inclined or are just plain lazy, I found a one-step modification: exchange the GZ for a Honda VT600C Shadow. It still gets about 60 MPG with conservative riding. Well, maybe.....test ride tomorrow. :biggrin:

[David Bo]

That is a nice bike... What model year are you looking at? I think they look kinda similar to the GZ but with a skinny front tire.

[Easy Rider]

That is a nice bike... What model year are you looking at? I think they look kinda similar to the GZ but with a skinny front tire.

An '07 with less than 2K miles. It appears that '07 was the last year for the small Shadows. Pity.
Not sure I will like the extra rake and skinny front as I'm sure it will handle a bit differently.
Other minor drawback: it is "girley RED". :biggrin:

[David Bo]

Red is not too bad a color... I have a friend that I used to ride with who had a PURPLE Shadow 1100 (a 2004 I think). Now THAT is a girley color! It had flames on the gas tank too. Holy crap... That bike cried estrogen!

[music man]

The severe drawback to the Shadow 600 is that it has a tiny gas tank on it, and combining that with the lower gas mileage it will seem like you are stopping every five minutes for gas (not that I wouldn't ride one).

And also that annoying gap between the gas tank and the seat, and that hideous big silver bolt sticking out, I don't know where they were going with that, (but again, not saying for the right price I wouldn't ride one).

[Blackbird]

The K & N Filter is SU-5589, I put it in Raven and it fits well. The main jet I'm using now is a 132.5 and it does well. I also picked up a 137 to try out later down the road, if at all. With my new exhaust and these alterations it pulls well up hills in a higher gear. Now I'm just cooking up more fun add ons for Raven, she likes it! Enjoy your GZ's .... that's why Suzuki made them for us. :2tup: :2tup:

[Easy Rider]

The severe drawback to the Shadow 600 is that it has a tiny gas tank on it,

And also that annoying gap between the gas tank and the seat,

I noticed both of those things.

Given that my old bones need regular stretching, 2 gal. @ 50 MPG makes for a stop every 2 hours; sometimes I don't make it that long.

I think my sheepskin gel pad will cover the ugly gap.

[David Bo]

Blackbird, did you change out your exhaust as well? If so, what did you put on?

[Blackbird]

David Bo ...Blackbird, did you change out your exhaust as well? If so, what did you put on?

Yes I did. An Emgo 26" megaphone exhaust (not Dunstall). A little bit longer than the stock exhaust. Has a community friendly, wife approved, sound. Go here for a peek ...
http://www.denniskirk.com/jsp/product_c ... Id=&mmyId= (http://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=446993&store=Main&catId=&productId=p446993&leafCatId=&mmyId=)

[David Bo]

Yep. That is the one I have on order. Did you install it yourself? If so, can you walk me through the cutting and swapping phase? I am a little nervious about screwing something up.

[Blackbird]

There is nothing to be nervous about. The "how to" from this site is what I followed, sort of.
viewtopic.php?f=8&t=19&st=0&sk=t&sd=a (http://www.gz250bike.com/forum/viewtopic.php?f=8&t=19&st=0&sk=t&sd=a)
Pull the heat shield off, only 2 screws. As you face the exhaust system your cut will be just to the left of the factory weld. I used a sawzall and a smaller hand hack saw (to get between the frame and exhaust pipe). I used new steel cutting blades which will cut through the outer layer of the muffler fairly quick. Make certain to stop (several times) and look to see that you don't cut through the inner pipe. Do this often. Even use the hand saw to do finishing cuts if you need to. Once you cut through the muffler it will easily slide off of the inner pipe. Don't forget to unbolt the back end of the muffler. I mounted the new muffler with the hanger, cut off the hanger what was not needed, used my grinder to round and smooth the edges and tighten the bolts down. The local muffler shop (2 blocks away) welded the new muffler on. $20 and maybe 10 minutes of time was all that was needed. Make sure they cover your bike near the area being welded so as not to burn your paint job on the frame. Also make sure that the muffler is aligned to your likening, then weld. Install the heat shield, it should fit fairly well.

[David Bo]

Thanks Blackbird... I just have to find a muffler shop that can weld it for me. I have access to a welder but it is a "stick" welder, not a mig welder. I believe stick welders will get too hot and burn throught the chrome. Did your EMGO come with a clamp?

I am wondering if I could use some of that JB Weld stuff where you mix the A tube and the B tube and then set the pipes in place (maybe with a clamp on top of the seam). The website says it works with temperatures up to 500 degrees F.

Does anyone have any thoughts on this???

[music man]

Thanks Blackbird... I just have to find a muffler shop that can weld it for me. I have access to a welder but it is a "stick" welder, not a mig welder. I believe stick welders will get too hot and burn throught the chrome. Did your EMGO come with a clamp?

I am wondering if I could use some of that JB Weld stuff where you mix the A tube and the B tube and then set the pipes in place (maybe with a clamp on top of the seam). The website says it works with temperatures up to 500 degrees F.

Does anyone have any thoughts on this???


I wouldn't trust JB weld to hold it, just picture going down the highway going 60 and your exhaust flying off. And yes unless it is a VERY experienced welder you will blow right through that thin metal (and even then he still might) with a stick welder.

[David Bo]

Yeah, that would make for a very bad day... However, there is a little hanger about 18" back from the weld area that would prevent that from happening (I think). That hanger supports the weight of the pipe and bolts the new exhaust to the frame. I think I might try this JB stuff if the new EMGO pipe comes with some sort of a clamp that I coul use as well.

[Easy Rider]

I think I might try this JB stuff if the new EMGO pipe comes with some sort of a clamp that I coul use as well.

David, buddy......we need to have a serious chat before you do something really ......mmm...unwise. :roll:

Forget the JB weld; it is little more than just epoxy glue. It will NOT hold but WILL muck up the joint so that it will be a double pain in the ass to weld later.

If you are going to do it, do it right.

[David Bo]

I hear you Pal... I will find a bike shop or a muffler place that will help me out. Thanks for the wisdom!

[patrick_777]

:plus1:

It may say "weld" on the package, but glue is still just glue.

[David Bo]

Hey, what if I buy some MIGHTY PUTTY? :retard: Billy Mays says it will do just about anything!

[music man]

I hear you Pal... I will find a bike shop or a muffler place that will help me out. Thanks for the wisdom!


Oh I see you will listen to Easy Rider but not me :cry: :cry:

[Easy Rider]

Oh I see you will listen to Easy Rider but not me :cry: :cry:

Gotta just keep piling on until the scale tips......... :roll:

[mr. softie]

I happened to use the JB Weld to patch a quarter sized hole in a diesel suburban exhaust manifold, out of desperation more than anything, and it held as long as I was driving the truck (over two years). But I agree that it has no place on a motorcycle exhaust.

[patrick_777]

Patching a hole is one thing...Using it to "weld" a muffler is another thing entirely.

[Blackbird]

David ... Your muffler will come with a hanger and a clamp. Some people will clamp instead of welding. I chose welding because that was my comfort zone. Try clamping first. Just make sure it does not interfere with the heat shield placement.

[David Bo]

Thanks again Blackbird... I will let you know how I make out withhmy weekend project! :skull:

[Blackbird]

David ... Good luck this weekend, take your time and do the job right. You can see what the exhaust looks like on my bike by going to GZ pics I just posted a few. Maybe it will get you enthused enough to get that exhaust job done. :2tup:
viewtopic.php?f=2&t=2353 (http://www.gz250bike.com/forum/viewtopic.php?f=2&t=2353)

[David Bo]

Thanks Blackbird! That Raven sure is purdy! I noticed that you did not put your heat sheild back on. Any reason in particular?

[Blackbird]

David Bo ... Thanks Blackbird! That Raven sure is purdy! I noticed that you did not put your heat shield back on. Any reason in particular?

Hey David,
Yes, I put it on. It would look ugly without it. The weld would stick out like a sore thumb.

[bassmaster]

i was wanting to also do a mod on my bike but were did u get the jet?

[bassmaster]

i was wanting to also do a mod on my bike but were did u get the jet?

[bassmaster]

sorry i didnt mean to post twice.