Topic: do I have to sync carbs changing slow jets

[miller_87]

Okay, here's the deal.  Ive been rejetting my carbs lately because of a Mac 4-1 exhaust I put on.  I finally got the carbs set so the engine was running pretty good accept on the low end.  I took it to the local mechanic to have it synched to see if this would help any.  He synched hte carbs, and it is running somewhat better accept on the low end.  Here's the thing, I changed the slow jets from the stock 40's to 38's, and want to put the 40's back in.  If i change those and turn out the idle screw 1.5 turns like stock, will I have to take it back in to get it synched again, or will this be okay?  My bike is a 73 cb500

[MRieck]

I know there will be those that disagree with me BUT I would would resynch. I've found changes to the low circuit,ie fuel/air screw changes etc  induces changes....period. Will it be enough to absolutely warrent resynch...probably not. I've found that every cylinder runs differently and having 4 carbs makes that point more evident. But I have the tools so it's not a big deal. Long and short...you'll be OK but I'm a perfectionist.

[Gordon]

I'm with Mike on this.  If you owned a carb synch, then I'd say do it, but if you have to pay someone else to do it, then don't worry about it. 

By the way, you should go out and buy a synchronizer.  

[MRieck]

I'm with Mike on this.  If you owned a carb synch, then I'd say do it, but if you have to pay someone else to do it, then don't worry about it. 

By the way, you should go out and buy a synchronizer.  

Gordon has more posts than me so his word IS gospel.

[Bodain]

I disagree with the others. I see no reason to re-sync merely because I changed the jets.

However.. Experience tells me. If I remove the carbs from the engine and fiddle with them. I must resysc.

Case in point. I had my carbs synced perfectly. You always know you have a good sync when you can get the engine to idle smoothly below the manufacter's recommendations. All I did was remove carbs and move the needles up one notch. Very rough idle after that. 15 minutes to resync and it's smooth as silk again.

Spend $50.00 for the sync gauges and do it yourself.