Topic: Are these Original Exhaust Pipes?

[cb650guy]

Hello All,
I have a 1980 CB650 Custom.  I am having problems getting the bike to idle properly and I would like to know if these exhaust pipes are the original. 

If you notice in the first two pictures the pipes on the left are different than the pipes on the right, the exit holes are much larger on the left.  Is it supposed to be like that?

If the pipes on the left and right are indeed different how would it affect performance.  The #2 cylinder misfires often and causes a backfire which shoots a flame out of the muffler also.

Here are the picture links.
http://imgur.com/tXBbg.jpg
http://imgur.com/bwl6O.jpg
http://imgur.com/eHVar.jpg
http://imgur.com/CCaui.jpg
http://imgur.com/LDPRD.jpg
http://imgur.com/VblEU.jpg
http://imgur.com/pKEby.jpg
http://imgur.com/YQNgh.jpg
http://imgur.com/muwW6.jpg

Thanks,
Adam

[Mainerider]

Hi Adam,

It's Joe.  No, the LH side is definitely not stock. On the top of the top muffler on the RH side (brake lever side) you will find the code HM460A; that is the OEM exhaust part code.  
If you are having problems with just one of the 2 cylinders running off that particular 2 into 2, it's probably not exhaust-related.  Afterfires can be caused by a host of reasons but usually it's caused by unburned fuel lighting off when it hits the hot header pipe on the exhaust stroke. So, perhaps you have a weak spark in the cylinder. I would start by warming the bike up and spraying each header pipe with water; is #2 noticeably cooler than the others? If so, it most likely is a bad coil, plug wire, or spark plug (or any combination thereof). There are other possibilities but these are the most common culprits.  Hope this helps.

[cb650guy]

Thanks for the response.  Even if it is not causing the backfire what other problems could it cause?

Yes, #2 is generally just warm when the other pipes are fire hot.  The cylinder is rarely firing, and I believe when it does fire it misfires.

The coil response for #2 also fires #3.  If #3 is getting a good spark does that imply that the coil is not at fault?

Thanks,
Adam

[Mainerider]

Let's work on the most likely first. Are your plugs old? Try swapping the #2 plug w another cyl and see if the problem migrates. If so its a bad plug. If it doesn't migrate then it could be a bad plug wire. Try the same test by swapping wires. If it is that I will send you a good plug wire along  with the other items. BTW, how many miles on the bike? 

[Mainerider]

PS
Yes coil is probably ok. Re exhaust, a freer-flowing pipe could make those cyls run lean but that exhaust doesn't look to be a substantially freer flowing than the oem exhaust.

[cb650guy]

Thanks for the responses.

When I get home from work tonight I will do what you suggested.  It is probably not the spark plugs since they are new, but it could definitely be the spark plug wires.  I will try it out.

[Stev-o]

Could also be plug cap, can be checked w/an ohmeter.

[cb650guy]

I did not have time to switch out the coils, however, I did measure the plug cap resistance values.  They were all between 4.25 and 4.5 kilo ohms.  Is that acceptable?