Sticking valve or? Hard cold start.

[Ceed Klumper]

My '76 has become difficult to kick start when cold, after sitting for a few days. When it finally does start, there is a clear ticking sound from the engine that disappears after maybe 8-10 seconds. If I stop the engine right then and kick-start it again, it fires up immediately, one kick, as it does the rest of the day. I also noticed when cold there isn't much compression. Once the engine warms up a bit is runs really smooth and quietly.

So it seems like a valve is sticking. Or could it be the chain tensioner? I have set all valve clearances as well as the chain tensioner clearance to spec maybe 500 miles ago.

All tips appreciated!

 

[xjwmx]

these make noises. the ticking after a few days of rest is probably oil slowly running off of parts. compression is higher with a warm engine and throttle held open. about 150 lbs is typical best. after warmed up, they do start quicker the next time,

try this trick. kick it two or three times with the key off and choke on and the throttle full open. then turn on the key and start normally. i've started mine at 27 degrees like that (and gone for a ride, with gathered crowds cheering). make sure you use choke and that it's working.

this could all be summed up as you haven't described anything yet that isn't normal.

 

[Ceed Klumper]

Thanks xjwmx. The odd thing for me is that, if I start it cold a day just after I"ve ridden it, it starts up during the first kick and there is no ticking noise at all. But if I wait a few more days, it will take 5-10 or even more kicks and there's a very loud tick that disappears after a couple of seconds. Also, this phenomenon wasn't there the first 10 months of my ownership, it recently started. When I say 'cold start" here in Southern California think 70 degrees these days.

 

[gggGary]

Recently I asked an XS'r if he was using the petcock prime position on cold starts, problem solved......
Depending on temp after 3-4 days of sitting typically needs prime if petcock seals are working good.

 

[5twins]

A '76 should have manual petcocks. They would have no "Prime" position, just on-off-res. You might check your choke feed jets to make sure they haven't become plugged of partially plugged. If plugged, the choke won't work and cold starting would be harder. They are located off to the side in the bottom of the float bowls .....

You can inspect them by just dropping a float bowl, carbs still in place. You can check to see if they're clear using this light "trick" .....

 

[Ceed Klumper]

Thanks 5twins. I cleaned the carbs thoroughly in the Spring.
The issue isn't, I believe, with the fuel or spark. It's that something, I am thinking a valve or the chain tensioner, is sticking causing not enough compression etc, leading to tough start. Identical conditions starting the next day, starts first kick, no loud ticking noise first 10 seconds. Leaving the bike sit a few days, all else identical, very little compression, loud ticking noise when kicking or electric starting, finally after much effort bike starts, loud ticking noise for maybe 10 seconds, then the tick stops, and then I can re-start it without any effort, one kick every time. The only direct link to the hard start is the loud ticking noise. No tick = super easy start; tick = get ready for 10 kicks. Appreciate all the suggestions, please keep them coming.

 

[GLJ]

Leaving the bike sit a few days, all else identical, very little compression, loud ticking noise when kicking or electric starting, finally after much effort bike starts, loud ticking noise for maybe 10 seconds, then the tick stops, and then I can re-start it without any effort, one kick every time.

Sticking valves would account for the low compression/hard starting and a loud ticking when first started.
Could be interesting to let it sit for a few days and then check the valve clearances.
Does the ticking sound like it's coming from the top of the engine?

 

[Ceed Klumper]

Thanks, yes, definitely from the top of the engine. Just tried it again, bike had sat since Thursday. Very difficult start, had to go electric, loud tick that stopped when I revved the engine, as has become the pattern. Shut it off, then a half a kick, really effortless, and she started purring, no tick.
Will do as you suggest, check valve clearances cold after few days and report back.
Maybe the tick is not associated with the actual cause, so will explore the carb/choke system as well it just seems more likely related to that ticking sound. When I am trying to kick start it, I can also hear the ticks, about 2 or 3 each kick as I am kicking the engine over, if that helps at all.

 

[GLJ]

When you check the valves make sure you turn the engine over 2 complete revolutions before checking any valves.

 

[gggGary]

Last time you set valves were any "way out" of adjustment?
Open valve covers, check the adjuster nuts are still tight.

 

[Ceed Klumper]

Thanks - when I checked the valve clearances as I recall three were within spec and only one I had to adjust, but only slightly. Ignition settings were also spot on so it seems the PO had that all covered.
I was wondering if it could be caused by the oil put in, Lucas full synthetic 20W-50 as I noticed it started to leak just a bit when it didn't before so it seems this oil is a bit thinner that what was in it before.
All original engine, never been opened AFAIK, 5,000 miles since new, I bought it a year ago.