Hi all fellow Yamaha owners,

I just picked up a beautiful 1986 Radian with ~26k miles. It was bought and priced as a not-running type deal. The previous owner said it hadn't been run in ~2.5 years. When I looked in the gas tank, I saw it was full of old gas and I feared the worst. I was getting ready to take the carbs off and apart, when I decided it couldn't hurt to try to start the bike. I tried, and it started right up. I was surprised.

Anyway, after fooling with it and giving it new gas, I have detected a few problems with the bike. It seems like cylinders #1 & #2 aren't firing. After running for a few minutes, exhaust pipes #3 & #4 are about 300F, while the other two pipes are between 100-150F.
I can feel puffs of air/exhaust coming out of each muffler equally. When I did a compression test (the numbers aren't correct but the spread is), I got 100psi exactly on every cylinder. I did the test taking out 1 spark plug at a time, and with the throttle at idle. I didn't know that wasn't the proper way. So they cylinders do have good compression, but the spread/difference is what's important.

I took the two questionable carbs off and took them entirely apart. Everything looked fine. I put them back together and still nothing.
I took the bike for a ride. At idle, it seems weird. CHOKE ON - the bike will idle freely and hang at ~5-6k rpm. I don't like it when engines do that. With the Choke off - it will idle at 3k rpm or sometimes lower.
So I left the choke off. If I took off in 1st gear, it would be fine until 4k rpm, then it would bog down. So I would pull the choke out, and it would surge then immediately bog down again. Then, I would go to switch gears, and it would shoot up to 7-8k rpm until I got into the next gear. Then bog down. It went through all 6 gears fine, but I couldn't get it above 25-30mph.

I thought maybe the air/fuel ratio on the carbs was bad, but I can't figure out how to adjust it.

Also, I think the timing chain is loose and slapping the valve cover. How do I adjust the timing chain? And how do I check/adjust valve clearance? I'm not at all familiar with these types of valves.


Thanks a lot for any input! I REALLY want to ride this bike because it's so cool! But, it needs to be running right first.

Check out BADRAD600.com, USA based Radian site, manuals and info etc

Its its not run for 2.5 years, then a service is advisable, oil/air filters/oil change/spark plugs/battery charged/chain cleaned and oiled and tension checked/brakes checked/cables lubed up. Check the carb to engine rubbers for cracks/splits, and that the rubber pipe from the same rubbers that goes to the fuel tap is good and not cracked/split/kinked. Check that the fuel pipe from the fuel tap to the carbs is good and not cracked/split/kinked. Check the air to carb rubbers are on properly and not split. The fuel tap on the Radian can be a problem, there is a filter on it inside the tank, if its not run for a while the fuel may have jellied up on the filter, and on the inside of the vacuum operated fuel tap.

Checks tyres for cracks/splits

Good luck with it, post a photo.

Be careful, the Radian is surpisingly quick with strong engine braking

Hi 1the cam chain is self adjusting

2 The valves are shim style adjusted ( requires pulling the cam shafts after measuring if wrong 2-4 thou intake 4-6 exhaust)

3 Don't mess with the air fuel scerws untill you find your vaccum leak,that is most likely why it's idling at 3k, try spraying wd 40 around the intake manifold 1 at a time and if the idle drops then you found it

4 Have you tried new spark plugs?

5 how in the hell did you take off only 2 carbs? They are on a rack of 4 as far as I know