The International CBX Owners Association

I’ll start with the obvious, check for vacuum leaks around the intake manifolds.

I had checked last time after the carbs were off and there were none. This time I only replaced the needles with the carbs on (and the engine lowered just a tad).
But I just remebered, where the headers go into by my 6-in-1 collector there is a small leak between header 5 and collector. I have tried to seal it off but wan't really able to get it completely sealed. Can that exhaust leak cause popping?

A handy diagnostic tool for for carbs and ignition is an infrared Thermometer Gun for Cooking, -58℉~1382℉(-50℃~750℃) Dual Laser Temperature Gun. My bike is popping too and using the gun with the motor idling quickly revealed
- #1 70 C 40C cooler <<<< misfire on # 1 cylinder why? carb or ignition wire
- #2 110 C - #3 110 C - #4 110 C - #5 110 C - #6 110 C
Note: focus the beams on the headers at the bend (black headers work better than chrome)
This method can also be used for fine adjustments of the air mixture screws.

-Scott

oroepke wrote: ↑

Wed Oct 18, 2023 12:41 pm

Can that exhaust leak cause popping?

Yes an exhaust leak will cause popping......

Re Scott's thermal camera observation - I'm not sure you'd get any meaningful data from a chrome downpipe because the emissivity of the shiny surface confuses the camera (basically you might get readings from the cold sky reflected off the chrome or other objects) - hence Scott's comments about black headers.
Perhaps if you did it in the dark you might be able to get comparative results - I don't know as I've never tried it.
This is probably not a very useful post but it was drummed into me when I did thermographer training how careful you need to be with shiny surfaces!

Simon

Yes, you could add a touch of flat black paint then remove it later.

My experience with an infrared Thermometer Gun is that you get quite accurate readings on the shiny header pipes, the importance is to place the infra red dot at the same location on all pipes.

Good input thanks. I had used my infrared thermometer before, but didn't see any significant differences between header temps. I wasn't aware though that the shiny surface impacts the readings. Anyways, in the meantime I have been able to fix that exhaust leak by the collector and that totally took care of the popping. Runs as it should now!

I have put around 200 mls on the bike and I enjoyed it a lot! A few things I realized though, the exhaust is too loud for me to ride more than 100 mls in a day and the Corbin seat is really low, which means there isn't much foam between me and the battery..... if I decide to keep the bike I will probabaly be looking for another seat and exhaust.

I also ordered the clutch rubber blocks and will tackle that clutch upgrade soon.

Just curious, what gas mileage is everyone getting? Mine was slightly below 30 on the last two tanks, but I admit I used the 7-9 k rpm rev range quite a bit, just because it was so much fun!

Attached pic is from me and my 18 yo son going on a ride (he owns a Duke 390) and this was his first time trying out a liter+ bike. He was impressed to say the least!

I have averaged 36 mpg the life of my '79. Any individual tank full may give 30 mpg or less, depending on how you run the bike. Get a stock reproduction set of pipes and you'll like the bike much better. Seats are too much of a personal preference to comment on, however, the several Corbins I've had have all been quite comfortable, though firm.

Dave

You might consider this for your saddle: https://airhawk.net/product-category/seat-cushions/ Works great on my 82. As for mpg, depends, as Dave mentioned, upon your wrist. My 82 will cruise at 75 mph all day and do 40 mpg. But, then, do have fun!! That's the whole purpose.

Dave, I am sure if I slow down a bit I'll get the mpg up . There will be a bike show in Burnet (60 mls from me) this Satutrday and I'll try to cruise over there a bit slower and see what happens "The" Kevin Schwantz will supposeddly be there! The Corbin is also vey low and since I am relatively tall, the seating position is cramped for me.

Larry, I had tried that airhawk pad on my R1200R a while ago. I didn't like that it felt a little bit like an air mattress and especially in turns I felt disconnected from the bike.

Have fun in Austin. Snow tickles here last night.

Best time of year starting now!

If the airhawk feels as if you're trying to sit on a beach ball, let most of the air out. It'll make a huge difference.

I think I have tried that too. Still wasn't for me. But that was 10 years ago, maybe I should give it another try!

Had an amazing 170 mls ride last Saturday. Bike runs great, plugs look great! I will tackle the clutch rubbers next, I'll start a new thread to report how it goes. Thanks again to everyone for their input on the air/fuel stuff!