Hitchcocks Forum

I know this is an old topic but just want clarification. I have just done away with the emissions junk on my 2006 65es, I am also just changing the standard silencer for a goldstar type. Do I have to alter the jetting in the standard carb, if so what to?

Jetting guide for mikcarbs on this page.

https://accessories.hitchcocksmotorcycl ... ttor-parts

Many thanks.

JohnnyS, If you have a read of my post on 6th Jan, I reckon changing the silencer makes little or no difference to the mixture and you could leave the jetting the same. Make sure you do a plugchop at wide open throttle though. Many will contradict this but this is how it seemed with my bike which is the same as yours I think. Any change to the air intake requires richer settings. I have tried to add a link to my post. Good luck.

viewtopic.php?f=3&t=11249&start=10

Whether or not you will need to re-jet and what re-jetting might be needed is always best decide not by charts and theories but by running the bike with whatever mods you make and taking note of how the engine responds at the four main throttle settings - idle, just opening throttle, mid-way and full throttle.

I know there are different ideas on plug-chop but I don't think they tell you much unless it's a racing motor cut at full throttle. Better to inspect the plug after a lengthy run. This will give a better indication of plug suitability and carburetor settings. In normal road use the state of the plug tip will not change suddenly - and a reading after a lengthy run will provide the best indication of the motor's state of tune.

It’s still important to check the mixture at all throttle openings. If you run too weak in the mid range where the needle jet is controlling the mixture you can still overheat the piston and it can happen surprisingly quickly. Although the piston might not get holed it can still smear across the ring lands which can result in the rings sticking in their grooves.

As far as the silencer making a difference to jetting is concerned, it surely depends on individual engines and where the “cork in the bottle” to gas flow actually lies. Changing the silencer on my 350 from the OE Indian made one to a “straight through”Gold Star pattern made a very noticeable difference, much more than changing the inlet side. This was the same with my other bikes, dating back to my very first one, a BSA I tuned in the 1970s.