Pitfalls of Smoothbore carbs?

[Anonymous]

I thought I posted this yesterday, but can't find it anywhere so I must have screwed up. All apologies if this is a repeat.

I am considering the purchase of a nice looking '79 GS1000 that has, among other things, smoothbore carbs. I understand these are a nice performance item, but was wondering what the ramifications are for driveability and reliability/maintenance when running these carbs.

The primary purpose of the bike will be for riding back roads, but since I live in the city odds are it will also get a bit of around-town use and the occasional several-hour cruise to other cities.

 

[Anonymous]

Smoothbores are great for performance. I prefer the stock carburetors myself for "just riding". I've noticed that midrange torque is better with smoothbores, but that quick snappy response and high end torque is better with regular old carbs. Of course opinions will vary.


Tim

 

[Hap Call]

I run Mikuni 33mm smoothbores on my '81 GS1100EX... I love 'em! They allow for some serious tuning (I run a little rich to keep the pinging down) and are stone reliable. The only down side is that they do not have accelerator pumps so when you whack open the throttle there can be a slight hesitation followed by explosive acceleration. The way around this is to just roll the throttle on. Someone on the forum said that you can tune out this hesitation by cam timing, but I have not been able to do it. But it really is not noticeable on my bike.

Hap

 

[Anonymous]

Thanks guys...

Assuming the bike is properly tuned, are there any issues with cold starting or any need for constant tinkering that these carbs typically bring?

 

[Hap Call]

Thanks guys...

Assuming the bike is properly tuned, are there any issues with cold starting or any need for constant tinkering that these carbs typically bring?

Mikuni smoothbores do not have a choke on them. They rely on an enriching circuit that adds fuel so that the mixture is rich enough for cold starts. Once I set my carbs up I never had to do another thing with them. Now if you have an air leak between the carbs and the head (i.e. at the rubber manifolds) you will never get the carbs to run right. So make sure your rubbers do not have leaks!
Hap