q's about jets. not 650 , well, kinda

[angus67]

http://www.mikesxs.net/products-38.html#products
Hi guys and gals! Was wondering if you all could help me on my carby problem with my 2003 Suzuki marauder.
A couple years ago, I did a baffle-ectomy to my 805cc Suzi, and sounds awesome!! Unfortunately, it stumbles and hesitates from 1/2 throttle to wide open. I usually pull out the enrichener before I run up a hill, but really getting on my nerves.
Here's what I've done to try to eliminate this problem. Have purchased adj. needles, and they are installed correctly, with proper spacers. This is the stage one cobra kit. It only came with needles and a drill bit for the emission cap. I thought that would be all I need, but, alas, 'tis needing a bit more fuel. These carbs are a total bitch to get at, one carb is under the gas, the other under the seat. This is why I've put up with it for 3 yrs.
I have been lately searching for some one with a similar set-up with a running bike. I found a guy that is running a baffle-ectomy, adj, needles, and 125 front MJ, and 135rear MJ. the stockers are 90 front, 100 rear. these are mikuni 36's. Now, the front jet is smaller in overall diameter than the rear, similar to Mike's smaller dia. and bigger dia. jets. See the link I pasted
My questions are:
Are all mikuni MJ's the same thread?
This jump up in size seems excessive, but its a better starting point than I had before.
even if the overall diameter is different, there is nothing in the way of installing the MJ's.
I'm thinkink about buying mike's jets. Ihave to get some for my 650 anyways.
Do you think this will pay off? Or is there significant differences in 650 jets compared to a more modern engine ? IE: needle seat, depth of jet threads.
Do you think I should buy a model specific jet kit, even thou they are way overpriced? Most come with needles, which I will have no use for.
Ive already tried richening it up by raising the needles, but it just pops, and snaps. Right now it has run its best in along time. This bike was a screamer till I tried to make it 'cool'.
I cant possibly afford shop time, but this is just killing me. the weather here in Washington state is gorgeous, and a friend has just bought a 2004 gixxer 1000. Sweet bike. 8k miles, paid 7k. near flawless, tipped over once.
I'm dyin' over here!! What do you think about this?

Its the one on the right.

 

[yamaman]

Have a look at the Sudco page, very good info there. There are 3 (I think) different type of Mikuni jets. So you'll need to find out what exact carb you've got & which jets.

Easy way to burn a hole in your piston, or an exhaust valve running so lean!
Yeah, rear cylinder runs a bit hotter, having no air flow like the front, so run a little richer to cool it down some!

The jump in size doesn't sound to radical, of course ideal jetting doesn't necesarily come with someone elses ideal setting. Sounds feasable, I'd buy a set of them & a set up & down from there too!

You don't mention pilots, I'd suggest going up 2 sizes & up 3 sizes while you've got your wallet out! While you've got your carbs out doing this, I'd drop the needles back to the middle for a start point.

Get used to pulling those carbs, it should take a few attempts to get right. No such thing as a free lunch.............But it's going to make a hell of a difference having crayfish for lunch instead of baked beans!

 

[angus67]

im gonna have to put a petcock in a 1 gallon gas jug for this. I know someone else's settimgs are going to be different , but I need a place to start.
I'm using this for help http://www.iwt.com.au/mikunicarb.htm
If i'm reading this correctly, my pilots are fine. figure 7 shows mains kicking in half throttle. thats were my bike stumbles.

 

[yamaman]

Do you think I should buy a model specific jet kit, even thou they are way overpriced? Most come with needles, which I will have no use for.
Ive already tried richening it up by raising the needles, but it just pops, and snaps. Right now it has run its best in along time. This bike was a screamer till I tried to make it 'cool'.

Everything is relative, when you change one thing, that often requires that you change another. You changed your exhaust, now you need to change your carb.
You know that your MJ is too small. When you change that, you might find that you need to change your jet needle & also your needle jet. Don't forget that your piot jet is supplying fuel the whole time. So every part is important at 1/3rd throttle & above. Float height is also important & must be correct.
Yeah, you could maybe save money by buying the right sized jets & getting it running better. But you might find it a hell of a lot easier to run the kit that was designed for your bike, needles & all. I would imagine that kit comes with a couple of different sized MJ's. So IMHO you need to either go with the kit, or be prepared to chase the right settings. You might get lucky, or you might need to pull them down quite a few times to get it bang on. My 2c, that's all, good luck.

 

[XS1961]

Ive owned 4 SACHS 800 roadsters that used that same Suzuki 800 motor & carbs.. First thing I did on all of them was to junk the standard silencers(mufflers) so I needed to up the jetting..Messed about buying seperate jets on the first one and it took bloody ages..For the others I just bought a DynoJet kit for about £60.No messing, half hours work and they ran perfect!

 

[angus67]

Thanks, xs1961. I think its best to go with a model specific kit. If youve had this same motor, you know they can pull pretty hard on the low end, a little weak at the top, though. a little gearing needed there. Iknow, baby steps.

 

[XS1961]

Its money well spent
Does the U.S version have the narrow chrome tubes attatched to the heads at the manifold to divert unburnt gasses to a valve under the seat? If so you ought to blank those off too

 

[angus67]

nope. it has a pair valve that looks like a big az air filter. I took it off once, didnt run any different. bike looked like something missing there, so I put it back on.