By Adventurescot
#86600
Hi There, last week I had a great run out to the Highlands of Scotland on my Classic 500 and it went like a dream as usual. However, next morning she struggled to start and once she did she was spluttering like hell and finally stalled and has refused to start again. On inspection I found compression gone and that both valves were slightly open. The rockers were tight on the valves holding them down at top dead centre. I loosened off the rocker bolts and compression returned and valves re-seated. Anyone any idea why this would happen?? I have now stripped her down and am trying my hardest to get the pins out in the crank area that hold the lifters but they seem solid. If anyone has any information or knows what has happened here it would be greatly appreciated. Thanks
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By Wheaters
#86602
My 2004, 350 Bullet Electra suffered from severe exhaust valve seat recession and the compression disappeared after about 50-100 miles. Resetting the valve clearances restored the compression each time and I became very quick at resetting them. I eventually stripped the engine and had a hardened seat fitted, instantly curing the problem for good.

Valve seat recession wouldn't occur on an inlet valve though....
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By stinkwheel
#86604
So a unit construction, fuel injection bullet? What year?

Don't they have hydraulic tappets? So they should be self-adjusting.

By valve lifters I presume you mean the cams?
By Adventurescot
#86605
Stinkwheel, its a modern 2015 FI model. It sure has hydraulic lifters with pushrods. I at long last have managed to get the hydraulic lifters out (what a hell of a job) I would think they are self adjusting. I have cleaned them out and am now hoping they will be ok on re-assemble. Why they did what they did I do not know. I wonder if the oil pump is pumping too much pressure??
I know what you mean about hydraulic tappets but its not like that. The cams are down in the gearbox area and hydraulic lifters with rollers run on the cams. These lifters are like tubes of about 20mm diameter with a piston inside and a small oil hole. The pushrods then sit on top of the hydraulic lifters. There is no mechanical adjustment at all which I find a bit strange. I can only think they are self adjusting with the hydraulic lifters
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By stinkwheel
#86606
My understanding is that yes, they are supposed to be self-adjusting through oil pressure.

I wonder, were those overextended, causing the equivalent of a tight tappet? If so, you'd be wanting to check that the drain/return is clear. If they weren't tight, I'd be a little worried if the valves stems are straight or the guides very worn. Or even a seized rocker? I presume there was plenty of oil up in the rocker area?

I've had older bullet engines drop a valve seat (and still run, albeit slowly) but we should be past that kind of QC issue by the time yours was made.
By Adventurescot
#86607
The hydraulic lifters sure were solid. I also thought it was worn valves but for both to stay open just seems a bit too much to believe. I only see 1 hole in the hydraulics which I presume is an inlet but perhaps as they move up and down there may be an outlet in the cylinder or something like that. I can only try and hope it will work once back together. The weird thing is it was hammered at about 60mph all the way home for about 70 miles and went great. Next morning she refused to start. Perhaps the mice got into the engine ;-) Mystery to me!!
By black fingernail
#86609
I seem to remember Ford motor co. having problems when they started using hydraulic tappets. They found the cause was the oil spec. was wrong, and they developed a 'special Ford' grade of engine oil, and that cured it.
User avatar
By Dan H
#86612
Adventurescot wrote:
Thu Nov 28, 2019 5:14 pm
The hydraulic lifters sure were solid. I also thought it was worn valves but for both to stay open just seems a bit too much to believe. I only see 1 hole in the hydraulics which I presume is an inlet but perhaps as they move up and down there may be an outlet in the cylinder or something like that. I can only try and hope it will work once back together. The weird thing is it was hammered at about 60mph all the way home for about 70 miles and went great. Next morning she refused to start. Perhaps the mice got into the engine ;-) Mystery to me!!
The hydraulic lifters will be almost solid, they compress very gradually when under pressure through the tiny bleed holes above where roller is, its difficult to see these unless stripping the unit down. As soon as you release pressure from the lifters, they will pump up, e.g. when the rocker bolts were undone. They run zero clearance so feeling that the rockers were "tight" sounds correct.

You also mention that once the rocker box was undone it felt like the compression returned, are you sure that it was not just the auto decompressor that is built in to the exhaust cam doing its job, by releasing the rocker box effectively bypassing the decompressor from the system?

In my experience, the hydraulic lifters are very good on these engines and cause little issues. As also mentioned, I always stick to the recommended 15W50 grade of oil in these EFI engines.

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