Carburetor Adjustment, quick guide by Roger.

[wayne]

This procedure contributed by member HGH770N (Roger) who has extensive experience tuning, restoring and repairing RE5's. It's different to Suzuki's final bulletin (9) on how to set the Port Valve timing. However, this procedure is effective in many cases and was similar to how Suzuki originally timed the PV. The move by Suzuki to an earlier setting of the PV involved other factors not necessarily related to smoothing the transition from primary to secondary throat.

Suzuki RE5 Carb & Port Valve Settings.- addressing the #1 issue with the RE5 carb, a hesitation when transitioning from primary to secondary throat.

This procedure can be used without the Carb pointer tool. I have used this rough basic method for many years on many bikes and seems to get most bikes running, principally to remove the hesitation (fine adjustments may take time depending on the jetting/air filter/compression of unit and elevation where you live).

1st: Checks should be done to rule out other potential issues. Compression test should be done to check all lobes are over 100 psi. Ignition static timing is checked and set @ 5 degrees BTDC & good spark. Drain the clean carb using the M12 brass bolt underneath. A cold engine is recommended.

2nd: With a clean & checked/adjusted carb with a new float bowl gasket and fitted to the bike with a good air filter, make sure all cable adjusters (including the one under the twist grip) are wound in fully and the Port Valve cover is removed.

3rd: Fully open setting (without the pointer tool). This may need 2 people. Twist & hold the throttle fully open. Look through the Carb Primary behind the choke butterfly and you'll see the Primary butterfly. This butterfly needs to be horizontal (fully open) when the twist grip is fully open. Screw out the pull cable adjuster on the carb (the one closest to the engine) until you can see the Primary Butterfly is fully horizontal. Lock this cable adjuster in place.


Image to be added soon..........


4th: Next, remove the Port Valve cover by loosening the single Phillips head screw. Twist the throttle slowly a few times while looking at the Port Valve mechanism to view its operation. You will see the lug on the throttle driven pulley come into contact with the lever of the Port Valve. This is the point at which the PV starts to open.





Now look over the Carb. Over the top, left side back of the Carb is the large 2ndry Diaphragm. Its activation rod goes down and connects to the 2ndry butterfly. The movement of the secondary butterfly is held by a "Limit Plate" that you can feel by reaching over the back of the carb and resting a finger from your left hand on. Twist the throttle a few times to feel this activation.






The importance here is that the 2ndry butterfly should start opening slightly before the Port Valve should starts opening. If the Port Valve was to open before the 2ndry butterfly, there would be no fuel for the rotor and it would stall or hesitate.

Finally, with your left finger resting on the limit plate (over the back of the carb), look at the Port Valve and twist the grip slowly (a second person is required). You should feel your finger on the limit plate start to lift, this must be before the Port Valve starts opening. Adjust the pull cable on the Port Valve (under the fuel petcock) so this activation is correct.





I have come across a few bikes with cables that will not adjust and seem the totally wrong way. I end up making the cables to suit (even Suzuki NOS cables are different).

Finally, take up any slack on the twist grip and then, very important, check and adjust the metering oil pump using the markings on the arm and casting.

Some general points. Bikes with good compression (120 psi +) I've found run better with stock jets between 88 and 90 PMJ. Bikes with lower compression I use 92 to 94 jets. Air filters affect performance, try a few different densities and see what works best. Here's an easy way to see what your actual fuel level is:

[typ110]

Great en clear contribution Roger, thank you!

[timpa136]

Really a great "how-to" along with the illustrations.

Wayne, I recall but can't find it, your "how-to" right down to the number of threaded turns?

[wayne]

I do remember something similar but it was about tuning Bulletin 9 (35 PV) without an angle gauge I think. IE feeling the limit plate movement and setting the port valve knowing that each full turn of the PV adjuster equaled X degrees.

Roughly I think it was each full turn = slightly more than 2 deg. To do a Bulletin 9 tune, it would either be match PV and limit plate and then tighten the PV about 3 full turns to set the PV at 35 (wind adjuster out) or, assuming you'd done the Accelerator Pump at 28 degrees as per the same Bulletin, time the PV to that and wind it in about 3 1/2 turns delaying the PV to 35. Either method was a ballpark and tune from there.

Anyone reading this though, remember that Roger's guide above does not use the Bulletin 9 settings and returns the settings to the original factory tune. So ignore this, use that.