Hello and Exhaust Question

[Yuedh]

Hello Everyone,

My name is Tim and I have recently aquired a 1980 CB750K.  I bought it "for my youngest son" to have his first bike.  He is just learning.  My first bike was the same except a 1981.  We are having fun with it and he is riding it very well.  I forgot how well these bikes actually handle.  It is really fun to ride.

Here is my exhaust question.  Can anyone tell me what exhaust system this is?  Also it only has about 14K miles on it but it is smoking.  What should I check first or how do I determine what the problem is?  Many thanks  

[Re-run]

hard to tell from the pic but the exhaust isnt what would cause you to smoke. If the bike has not been run in a while, the rings could just be frozen. Do a little flogging on it and see if it clears up.
You also did not say what color the smoke was.

[Yuedh]

I didn't mean to make it sound like the smoke was related to the exhaust.  I am just wondering what the exhaust system is.  The reason I am wondering is because I don't know if I need to put a jet kit in the carbs or not.  It generally runs smooth until you get to about 6k rpms then it spits and sputters.  It has to be coaxed into going higher.

On the smoke side.  I think it is a gray or maybe white color.  I wouldn't call it black.  The previous owner said it is running rich.  I am just not sure about those things.

Thank you for the response.

[Yuedh]

and what is flogging?

[Myumi-2]

To flog in Australia can mean to steal, to sell or in this context I think he means take it for a run and open the throttle.

[Re-run]

Flogging would mean to run the piss out of it! A simple test if the bike is running rich is to pull out the air filter and see if the problem gets better. Of course this is not a permanent solution, just a test.

[woodsrider250-2]

Looks like a MAC exhaust.

[Yuedh]

Thanks for the help.  I will pull the filter this weekend and see what that does.  If it is running rich, do I start with doing a good cleaning of the carbs?

Also thanks for the ID on the pipes.  That leads to my next question.  Is there anyway to know if the right jets are in it?  Or should I just purchase a stage 1 jet kit?

Appreciate the help.

[Myumi-2]

On carb number 4 you will find a number.  

Correlate that number with this list, http://www.hondachopper.com/carb.specs.html

and then you will know the original specs for your carbs.  On the jets they have their number, i.e 110.

Then try this for a walk through on how to clean and/or re-jet.

cheers
Tim

[woodsrider250-2]

If you pull the filter on these VM carbs it will run like crap guaranteed.  What color is the smoke?  Black is gas.

[Yuedh]

Was there supposed to be a link for the walk thru for cleaning the carbs?

[Re-run]

The idea is if it is already rich, removing the filter may help show that. The air box goes back on, it is not left off. So the test still works as intended.

[woodsrider250-2]

I hear ya re-run your theory is right on, but airbox/no filter on these DOHC VM's and the bike still won't run.

[Re-run]

Then I had a weird one, it would run without the filter but DID need the airbox.

[woodsrider250-2]

Interesting.....It's always worth a try!  Like I said I agree it's generally a quick trick to test...