Hi, Guys, I'm new in here...

[Daniel-from-Quebec]

Just got myself a nice XS 650 Special 1980 , I've been riding motorcycles for 50 years, but this is my first vertcal twin .
I know very little about this particular model, My bike starts and runs good, but when the engine gets hot, the idle rises, it can go up to 2,800-3,000 RPM... Any idea what i should check first ? Thanks

 

[Jan_P]

How high is the idle cold ?

 

[motormike]

Possibly the rubber carb manifolds are an issue... once hot they expand and allow air to be pulled into the engine.... perhaps when this happens.... leave bike running on center stand... let it idle down and direct starter spray at the manifolds.. see if it picks up Rpm's... Nice bike... Sportster mufflers ?

 

[nj1639]

A change from a restrictive to a more open exhaust without making the oft times necessary changes in the carbs main and pilot jets too could result in a “hanging when hot” idle.
Nice bike and welcome aboard!

 

[Daniel-from-Quebec]

How high is the idle cold ?

1200-1350

 

[Daniel-from-Quebec]

Possibly the rubber carb manifolds are an issue... once hot they expand and allow air to be pulled into the engine.... perhaps when this happens.... leave bike running on center stand... let it idle down and direct starter spray at the manifolds.. see if it picks up Rpm's... Nice bike... Sportster mufflers ?

Dunno where the mufflers are from, just bought the bien..

 

[Daniel-from-Quebec]

Dunno where the mufflers are from, just bought the bien..

Juste bought the bike

 

[Kevin Werner]

The ignition advance kicks in around 1600-1800 rpm. That exacerbates the problem of slightly high idle . It becomes a feed back loop to ever higher revs. If the carbs are still fitted with stock jetting you will be a bit lean with the free flowing exhausts. If the carb boots do not leak via the starter fluid spray do not despair. The main amd pilot jets can be changed without removing carbs. Find the tech section, top of the page. The process is a little bit fiddly the first time you do it but becomes second nature quickly. Lovely bike, welcome to the XS650 madness.

 

[5twins]

It appears that bike has points? If so, that means it has an advance unit and advance rod running through the cam. Both may be in need of servicing (clean and lube). When they dry out, the advance unit can stick in the advanced position and that can cause the idle speed to go higher.

 

[Kevin Werner]

Mains and pilots are a modest expense. Nichecycle parts has genuine mikuni jets at ~$5 each. You will get flamed here if you use substitutes. Non mikuni parts have a history of being wrong..

 

[Kevin Werner]

https://www.xs650.com/threads/carb-jetting.283/
Do yourself a favor and scan through the thread above. There is a ton of experience here bit we do appreciate that you get a little familiar with your situation. Saves a lot of back and forth questions. Also, pics are important. Cheers.

 

[Jan_P]

Idle cold OK
I would test Motor Mikes thoughts there are clamps that can be tightened
and a flange with gasket to the cylinder
And check the filter seal also
And then the starter fluid test

Inspect so the advance unit is working if it has points

Maybe the to lean suspicion can be tested with choke

 

[member43148]

I don’t see a points wire after zooming in there ?
It’s an 80

 

[Elventrip]

Welcome, Daniel! Awesome to hear you got an XS 650! High idle after warming up can be frustrating. First, check if all the clamps on the carbs are tight. Leaks can cause the RPMs to rise. Also, inspect the gaskets and filter. Sometimes it's good to test the carbs for cleanliness. Good luck!

 

[Lou_TX]

Hello Daniel from Quebec! I am Lou from Texas. (it seems that the XS is everywhere)
Welcome to the club!
Lots of smart and friendly people here for sure. You picked the right forum.
Nice bike and good luck with your idle. I'll have to watch the progress here to see the resolution. I am curious what is causing your high hot idle.

 

[46th Georgia]

Just got myself a nice XS 650 Special 1980 , I've been riding motorcycles for 50 years, but this is my first vertcal twin .
I know very little about this particular model, My bike starts and runs good, but when the engine gets hot, the idle rises, it can go up to 2,800-3,000 RPM... Any idea what i should check first ? ThanksView attachment 332138

Welcome to the forum.

 

[Daniel-from-Quebec]

Idle cold OK
I would test Motor Mikes thoughts there are clamps that can be tightened
and a flange with gasket to the cylinder
And check the filter seal also
And then the starter fluid test

Inspect so the advance unit is working if it has points

Maybe the to lean suspicion can be tested with choke

Thanks for the useful hints, my high RPM idle problem got away after i tightened the clamps , I would never have tought of that myself,
Just glad i joined this Forum !