gs450t carb questions.

[GmanGS450]

I have been tweaking my carbs for the last month, and just when I think I've got it. WHAM, a new issue. I have 2 to 1 shortened exhaust, pods, 40 pilots, 140 mains.
I pulled the plugs on the mixture screws and am currently running them 2 full turns out. Needles are spaced by 3 washers.

It idles great and runs to 5k, or half throttle. Then boggs to kill up to WOT. I had it running a few weeks ago but it started poping and backfiring so bad I just decided to add more fuel. Well that didn't work.

Any suggestions?

[pete]

With these CV carbs you need to tune from the main jet down (I made that mistake too).

Get your main jet right at WOT first, then do the needle, then pilot.

Do you have quality pods on there?

See if this thread helps at all:

http://thegsresources.com/_forum/sho...ng+jetting+450

[GmanGS450]

Thanks, I had the main jets figured out first, I thought. Now this...

I have new UNI filters. Foam. I had old K&N's, but in the mean time I am using the UNI's.

[pete]

I think the UNI's should be ok, at least that's what I hear... personally I went with K&N's but that's mainly because that was also the easiest to get my hands on.

So what changed between when you thought you had it and when it went pear shaped?

[GmanGS450]

One hot ride home from work. It was riding good, not great at WOT and I was able to use it everyday. Then one day riding home from work i cam off the throttle with a big back fire, then sitting in traffic it kept burping. Then it was really bad the next day when i fired it up, it would pop and backfire with no power over 4.5K. I had to pin it, to get past the dead spot and still it could barely pull me at 60mph in 4th gear.

last night I did some work.

Set the mixture screws 2.5 turns out.
spaced the needles with one more small 3mm washer. and tapered the needles with a drill and sand paper. using my caliper to check the size of each. Both needles taper from 2.05mm at the tip to 2.80mm- 20mm from the tip. I was able to sand a little then check... etc long process but it helped my dead spot.

Iam very close to just giving up on these. I have two nice VM32's sitting in my shop, but they are two stroke snowmobile VM's and the jetting its way too big. Also it seems like the stock GS boots are too large. I may just spend the money and buy two fresh VM32 from Dime City instead of messing around more with the CV's or the two stroke VM's.

[pete]

Hmmm ok you got me on that one... dirty fuel maybe?

I'm wondering if maybe it's ignition related?

Do you still struggle to get over 4.5K RPM?

If so, I'd probably pull the timing cover and make sure your advance mechanism is still moving freely and springing back properly.

I don't see how that could suddenly happen with a back fire but might be worth a check...