Suzuki T500 deceleration surging

[kenintheuk]

Hi, can someone out there please help me. I have a T500 that has the most violent deceleration surges you can imaging. The bike is perfect otherwise and I have no wish to let it go but can not live with this. New crankshaft and seals fitted. Cylinders rebored, new coils, plugs, points and condensers fitted. Timing is spot on checked both static and dynamically. Carbs are synchronized and checked with a carb balance. Have tried going both up and down plug temperature range. The slides do not stick and standard jets are fitted. Tried every setting on the air screws - my only clue is the further out it is the worse it is. Some improvement can be made by having the slides bottom out shut using extra springs and no tick over. Any sensible suggestions gratefully received.

[karl pa]

Could be an air leak on intake like carb rubbers, but most likely you may need to change pilot jets,it sounds like a lean condition.I think standard are 30,you can try 32.5 or 35, on my 75 I went to 32.5 which solved the problem

[Monkey man]

i have similar issues with my GT750J
Goes well otherwise but on the over-run is very snatchy

[karl pa]

i have similar issues with my GT750J
Goes well otherwise but on the over-run is very snatchy

I believe the 750J&K, you can use the mixture screws to smooth surging, they surge when they are to lean or to rich. You want to be sure chain is not to loose, carbs are balanced, and idle is not to high. Unless your not running stock pipes or airbox. Then you may need bigger pilot jets.
This past sunday I took a ride on my 750L, (which are known for surging) It was surging so bad I almost turned around. But after turning mixture screw for more fuel and dropping the idle to 800-900 rpm, it was a pleasure to ride.

[Monkey man]

where can i buy bigger jets for the 750J if i decide you go down this route ?

[karl pa]

I got my 32.5 jets at my local suzuki shop,but you should be able to get them wherever they sell mukuni jets.
And good luck getting the air box boot back on, they can be very trying of ones patience.

[joolstacho]

Pretty classic symptom of RICH mixture isn't it?
We used to diagnose a rich mixture by seeing if the engine surges when you close off from WOT.
Not sure about these carbs, but the theory was that backing off the throttle a bit drops the needle down into the main jet a bit which LEANS the mixture and it briefly goes faster (surges).

What's the performance like throughout the rev-range?

Have you tried it with the choke? That's how we diagnosed a lean condition... Adding a bit of choke at WOT richened the mixture briefly.

NOTE: I claim no special expertise apart from 50 years mucking around with these things.

[GTandcbr]

Make sure your chain and sprockets are in good condition and the chain is properly tensioned as this can also make the problem worse.

[Alan H]

where can i buy bigger jets for the 750J if i decide you go down this route ?

Bluesmokebaz. Ebay or kettleclinic.co.uk

[tz375]

They are normal Mikuni pilot jets. Try Jets R Us or your local dealer or Mikuni supplier.

Shudder on decel could be too rich or too lean, but usually it's too lean. Try adjusting the air screws to see which way makes a difference.