Switching carbs.

[murcada]

I'm wanting to make my KX500 a little more trail friendly and am considering replacing the stock carb with a Keihin "Air Striker" 38mm carb.
I was wondering if you guys had any experience with the "Air Striker" line of carbs and what you thought of them? Also, what kind of power changes could I expect going from a 39.5mm carb to a 38mm? Thanks for the help!

[mikesmith]

Your question reminds me of the KDX 220,its a great trail bike but under carburated,so serious riders bore the carb out bigger for more power!What Im getting at is wouldnt a fly wheel weight,and a Moose spacer be a better choice?I run my KX500 on fast wide open fire roads to the tightest single track you can imagine with only a V-Force reed as my only engine mod and it handles the tight stuff well,I will try the fly wheel weight in the future as every one who has in the woods loves it and its cheaper than a new carb.If you arent worried about max power and top end and only ride in tight woods and  want to try a smaller carb Id only go to the nekt smaller size,you will get better gas milage,low end will be more tractor like, but top end will suffer.Sorry I dont have any info on the type of carb you want,at one time I think it was Krause Racing made a kit that bored out your stock carb,then they had differant size venturie sleeves you put in to make your carb larger or smaller and was cheaper than a new carb,hope I helped a little.

[John]

The principle in general is; the longer distance between the cylinder and the carburetor - the more the torque-band moves to the low-end. This is the major mod (and smaller diameter on the carbs) on the Varadero engine compared to the Firestorm. The same principle is also applicable on a two-stroker (Moose spacer kit). The trade-off for this is less responsiveness; however it could be desirable on the KX500 sometimes.

The smaller diameter on the carburetor - the less (potential) maximum effect. Restricting the diameter will eventually be the limiting factor for air/petrol flow in to the engine. However a smaller diameter would also give you more control and move the torque torque towards the low-end.

I have changed to a V-Force reed cage mainly on others recommendation. There is a noticeable difference. More power all through, especially noticeable in the low-end. I would think it is cased by a better design than the stock one.

I have mounted a Moose spacer kit, again a change for the better. More torque and a smoother power delivery.

/John