Topic: poor running honda CB350F

[beeman]

having bought a honda CB350F that hadnt run for over 10 yrs and having no mechanical experience some may say I have bitten off more than i can chew. Changed Plugs and oil, air filter was filthy and stunk of fuel(I`ve a new one on order), cleaned carb bowls, new battery and  new tyres. Took it for a run and it was misfiring and lacking power. After 2 or 3 miles it died on me. After sitting side of road for 1/2 hr started up again and limped home.
 After getting a clymer manual i went about setting the valve clearances. to my surprise there was no clearance whatsoever which would go a lot to explain the poor running. Yesterday I went about setting the valve clearances. Following the manual I set clearances on all but cylinders 2 and 3 exhaust valves as  i couldn`t get a setting despite unscrewing the adjuster fully. I screwed them back in to visually match other exhaust valve adjusters and reassembled. Bike started instantly, runs smoother and accelerates faster, all in all a marked improvement. However I would like an explanation why I cant get a setting on the exhaust valves on 2 and 3.
 Thanks in advance for your input.

[two40]

Have you adjusted/checked points?

[Flyin900]

With you opening statement about limited mechanical experience I would speculate that you haven't been rotating the crankshaft and the corresponding cam shaft positions correctly.
I have never seen where all the valves had incorrect adjustment with no measurements that were even close to spec. Not being able to get any adjustment on the two cylinders also tells me you had the cam position on the valves/adjusters in the wrong spot.

Do you understand the procedure of getting the piston to top dead centre on the combustion stroke of that cylinder? Both the intake and exhaust valves will have some play on the adjusters when you wiggle them side to side that will indicate that there is clearance. The crankshaft/cam will be in the wrong position when the piston is at TDC on the exhaust stroke as the exhaust valve will still be under tension.

Usually the correct procedure outlined in the manual states setting the one cylinder on TDC on the compression stroke and adjusting those valves first. There will be a few other intake or exhaust valves on other cylinders that the cam lobes are not putting pressure on that specific valve. The valves on these cylinders are usually outlined in the service manual noting you can also adjust these specific valves too at the same time. Adjusting these specific valves at the same time eliminates the need to do each cylinder at TDC on the compression stroke and making the job a little easier and shorter to do.

[beeman]

in reply to two40, i have not adjusted points as when checked they were ok


in response to flying900, I am pretty positive i made no mistake in rotating the crankshaft and corresponding cam shaft. I`m pretty confident I understand the procedure of getting the piston to TDC.  I went to TDC 1/4 , checked for play on cam followers on cylinders 1+4 and there was no play play whatsoever on any followers. Therefore, unsure of which cylinder was at TDC I had a friend turn the crank while i looked into the valves. I could pretty much get close to TDC just by watching the valves visually,  On deducing which cylinder was at TDC I backed off the adjusters  a full 6 flats before I got play between them. Cranked 360degrees and then similar adjustment on cylinder 4 as I`d done on cylinder 1. Then moved onto cylinders 3 + 4. After adjusting all tappets I checked settings in order of firing order (1,3,4,2) and with the exception of exhaust valves 2+3, the settings are great. I removed the locking screws and adjuster on those valves to check for wear but they seen ok. With adjusters out the valves were touching the adjuster holder.
 Despite this the bike now starts first go, revs through the range and is smoother. My assumption with the rough running is the fact that the valve adjusters had been screwed down too  far and that the valves hadn`t been opening or closing sufficiently for the fumes to escape thus causing overheating, rough running and poor starting. All the symptoms of tappets being set too tightly according to searches on web.
Thanks for your prompt replies, I`m 99.9% sure I have set them correctly. Any advice greatfully appreciated!!

[beeman]

update:- just returned from 10 mile ride, No cutting out and smooth acceleration, none of which was possible pre tappet adjustment. Killed the engine when I got home and started it right away first press of the starter, again this wasn`t achievable pre tappet adjustment. Still have concerns regarding not being able to get a setting on 2 and 3 exhaust valves. Any ideas anyone/flying900?

[camelman]

beeman, I didn't quite follow your procedure, but this might help. When I adjust valves and don't feel like finding TDC, I rotate the engine with the valve access covers off and watch for a valve to depress. After the rocker comes back up, I rotate the engine another 20 degrees, and then I check the tappet clearance. As long as the screws on the valve adjusters are not stripped, this should work for you.

[beeman]

thanks camelman, I will try setting them again, following your procedure.

The problem with cylinder 3 and 3 exhaust valves are that as i unscrew the valve adjusters at TDC the valves keep rising with the adjuster. I have had the adjusters out and they aren`t stripped. The other 6 valves adjusted without a problem.
As a precaution I will double check them all again, thanks again for your input.