Zip-tied both ends with no change...I eagerly await my jets.

I missed it, what size jets are you changing to? Also, you aren't messing with the nipple jet are you? That one I almost changed on mine, fiddled with the main carb jets for a while and eventually got it dialed it right on with the bigger nipple jet.

Might be picking one of these up tonight. Depending on the shape, I will either get it running or part it.

So my Jetting kit arrived. Its one of the 6 sigma ones from Ebay.
The kit came with 3 leaner jets for the primary carb and drill bits to richen the secondary carb. There are a bunch of notes and some shims for the needles too.

I will start with stock needle positions and the leaner main jet for the primary carb...hopefully it all works out.

Thesyk- did you buy a bigger nipple jet or did you drill one out? If bought, were did you get it?

My nipple jet is the stock one (the size currently escapes me). And from what I understand, as long as you have the primary carb jetted properly and have them carbs synced properly, you are golden. However, regardless of what the Clymer manual says about how to sync them, if you have a set like mine, just getting them to a point where you don't have the "bog" when the sececond carb starts to open is a complete PITA.

It literally took me hours to get the sync right once I determined that I had the jetting right. And once you can rev all the way through, rough or not, you're close. Then it's a matter of getting the sync dialed in.

So I put the 130 jet in. The bike pulls 15% harder down low but the top end is still the same...I still hit this revv wall.This mean I have to try 1 size smaller I guess. Down to the 125 and see if it behaves the same.

Thesyk -Hmmm...I'm starting to think this whole thing is just like your issue. can you take a couple of minutes and clarify what you mean by bog? I'm wondering if its the same feeling as I get with my "rev wall". did you have any tricks for speeding up the sync process?

For whatever reason I was thinking that this was a jet the primary carb, then jet the secondary, then sync system. IT appears that this is incorrect thinking. I have to jet the primary till it runs right down low-mid range then try to sync the secondary till it works. I know I can richen the secondary with drill bits but I hope I don't have to.

The short and sweet of it is, the "bog" is the bike being too rich. Try this...

Drop your Main down to 125 so it's running lean (for the sake of experimentation)

Create a fuel IV (like what people in hospitals are attached to), hang it on your handlebar and connect it to the carb. This way you aren't dealing with having to work around your gas tank. I cut the bottom off an Aquafina bottle, hung it upside down, drilled a hole through the cap for a small hose to fit in and taped it to a wire hanger. It literally looks like your bike is on a IV!

Connect your IV to the carb, add a little fuel and cover with a rag so the fuel doesn't slosh around when you kick the bike to start it.

Loosen the sync screw lock nut

Start the bike

Turn the sync screw ALL the way in and rev the bike.

Turn the screw back out 1/4 of it's length and rev it.

Turn it another 1/4 and repeat.

Do this until you you notice that the rev gets clean since you are adjusting the timing for when the secondary carb is engaging. If and when you start to notice that you have a low end and a high end rev (even if it sounds like crap overall) the next step is dialing in the sync so that the PERFECT amount of fuel is delivered at the appropriate time from BOTH carbs when needed.

Let me know if this is at all confusing...

One more thing Tim (I discovered this today) if there is any possibility that the bike is running LEAN, try using the choke just a little to see if you get that rev you're looking for. I just discovered that my new bike (2003 WR450) is running too lean and just sounds like crap because of it. Just another idea for the troubleshooting toolbox.

So I plugged in the 125 today and did a quick run. Same thing, a little more power and a little higher rev but still not perfect.

I will try the 120 next, then try to fix the sync. I will clean up the plug to see if I can read it  with these new settings. I am also going to try to get a video of the bike hitting this rev wall so that you guys can hear what I mean

I don't think its lean as the choke make no changes.

I'm very sure that the sync will shed light in your problem.

Okay so here are the videos of the bike revving out. The first video is while I'm at a stand still and the second one is while riding and really holding the throttle open at the rev limit so you can hear the mis-firing:





Let me know what you think!

I tried to post this on your video...

That is almost certainly your sync. The fact that you can get the rev as high as you have it means you are pretty well jetted properly. Now you gotta get those two little buggers to work together properly!*It's a very fine balance in getting that second one to start opening at juuuust the right time.

I still want to try 1 jet lower...I may as well as I have it in stock.
Then I will play with the sync. I will also swap the spark plug for a clean one so that I can see what it looks like after I run it.

Be careful with that! Running a bike that size too lean will dramatically increase your engines temperature and possibly damage your engine. Remember, it's air cooled so you need to be careful with that. I still suggest leaving the jetting as it is and messing with the sync. You're practically there with the way it sounds now!

have you tried to run the bike with the digital tac wiring removed?

that video to me does not sound like the carbs it sounds ignition realated...
When I had my xt600 w/ tt600 engine the only thing remotely like that sound was a hickup when the secondary kicked in ..and it would only hickup 1 time in the transition.


depending how the electronic guage is wired it may be causing interferance. . remember with no load the engine ought to rev out higher with only one carb and it would be popping from the exhaust too..

I would get the multi meter out and check coils, cdi, and stator.. if you have a bad stator I believe I have a stator and flywheel left over from my tt to xt conversion

I have tried it without electrical loads (not speedo, lights) with same issue.
I have tested out all the electrical and its all good.
I have fitted my other CDI and it runs the same.

I'm confident that its jetting as the main jet size has changed the amount of power and the "height" of the rev limit. Also applying a vacuum to the float bowl allows it to rev higher

I should mention that I pulled the plug last night and its white so I have to eith go back up one jet size, increase the jet size on the secondary or start playing with the needles.

Yup... Like is said, the rev says that you are more than enough lean. The only needle that might have tha ability to adjust is gonna be on the main. The secondary one is static.

At the RPM you show in the videos, it sounds like the starving for gas. I had the exact same problem with mine as I worked to get that sync dialed in.

Easiest way to do this is to make that IV, and play around with it. You can putt around the neighborhood, stop, adjust, putt, stop, adjust. As long as the engine is hot, you're rounding third my friend!

Then that's the plan Stan

PS- both needles are adjustable. I figured this out the other day. On the secondary, you have to remove the set screw and pull hard to pop it out. You can also tap it out from the top of the slide. It sits in a little carrier

Just ringing in here after reading this entire thread...it sounds like you are lean. Somehow you do not have enough fuel at WOT.

Ran into your posts on your tt600 build great job! I sure miss mine. its a great bike   Tim