72 with issues

[Ludlow]

Hello folks,

I recently started riding my 72xs after bringing the paint job back to as close to factory as possible. Since my tank was at the body shop, maybe not the best first move, I hadn't had the bike on the road yet. I started it before sending everything off, and the compression was great... but...

While the cosmetics were getting done, I went ahead and rebuilt the carbs (diaghrams looked like new), adjusted the valves, set the timing, put the angular contact bearings in the steering head, and anything I could afford while waiting. Now she's back together and on the road. Well, she was. My first issue was poor performance after warm up. It behaved as if the left cylinder quit firing. The bike had half power and I was getting popping out of the left pipe. Idle was fine, but nothing else. I tripple checked the float level, but it was right at 25mm both sides. No leaks in the floats, I even popped the bowles off while full and they appeared to be at the right level. Inline filters are flowing freely and the plugs weren't fouling.

Yesterday riding home from work the poor performance was making me crazy. I pulled the choke on and suddenly had my other cylinder back but with popping. The other thing that started was a top end whinning that got louder and louder durring the 10 mile ride. It changed pitch and volume with the RPM. Oh-no - bearings (?). When I got home I pulled the plugs and they were gas fouled due to the choking. I retentioned the timing chain thinking/hoping that was the source of the noise. Then, when resetting valve clearance with the plugs out, I noticed turning the motor over by hand was rough. That's what really concerns me. Turning a motor over by hand with no spark plugs should only give resistance from the crank counterweight, right? This felt choppy, like something hanging up.

After all these adjustments and engine cooled down, the high pitch noise was still there. I can barely hear the exhaust over it. It seems to be coming from the front or top of the engine. And the left cylinder is still giving me trouble.

I'm hoping that I don't have to pull the engine and rebuild, so I'm posting this to see if any of you have experienced this set of symptoms. Could it be a fried cam chain tensioner? Why the whine? Compression still rocks, so

Thanks for any pointers. I guess the worst case is pulling the engine and going through it. Sounds like most of you guys have done that before. How hard can it be?

 

[PhatTony]

A couple things come to mind. Recheck your valve clearances. Might be too tight causing the left valve not to seal and cause the popping. The whining noise may be the cam bearings in the top end going bad or not getting oil. Easy way to check (and messy) is to remove the two bolts that hold the oiling tube to the top end and see if it's pumping oil up there.

 

[Ludlow]

I thought about loosening those oiler bolts, but then I saw how much fresh oil was on the valves when I was adjusting. Isn't the line that lubes the valves the same line that lubes the cam bearings? That's what made me think the cam bearings were done. Oiling was the first thing I thought about with the whine and the first thing I checked when I got home was the engine oil - just under the full mark. Then I started thinking about the posts warning about plastic in the oil screen from the cam chain tensioner getting chewed up. Could that impede the oil flow to the cam?

The PO said this bike was in his barn for 20+ years, and based on the condition of the chrome and seat, I believe him (no offence inxs). The paint restoration was to cover up a bad custom. The cam bearings are way up top, so if it had been sitting for years, no oil. This may be a side effect of 'barn fresh'. Also, if the compression release was too tight for all those years, could I be experiencing a sticky valve, even with great compression?

If I wanted to loosen the cam tensioner to manually crank the engine with no plugs and get a non-restricted feel for bearing condition, should the tensioner be sticking out of the adjuster? I adjusted so it was flush per the manual before turning by hand. Could I have overtensioned? These situation always cause me to second guess myself and the manual. Again, that's why I'm posting.

 

[addison]

hi Ludlow , I have a 72 as well and a similar thing happened to me. My bike had been stored for about 15 years when i brought it out and started it up it and ran fine for about a week save for a backfire problem on the left side , while i was trying to get the carbs to play nice I thought i would do all the maintenance in the manual including " adjust the cam chain " which i did according to the book but the knowledgeable folks on this site have informed me that one should tension the chain with the engine warm opps. I had done mine with the engine cold and ended up with the plastic/rubber striped off my cam guide.It was making a horrible whirling noise from the front of the motor and sounded like a bearing with no oil. You may want to check your oil sump for those plastic bits, you mentioned you retensioned the cam chain , did you you do that cold ?I am not exactly sure why it needs to be done warm but i am sure some one on the site who knows what they are doing will be able to explain why. If you check some of the older treads on cam chains there is also a way to tension it with the motor running. I cant say for sure that my tensioning the chain cold was the cause of the degradation after all the bike had been sitting for 15 years but i wont tension it cold again.
I hope you get it figured
peace
Addison

 

[gentlemanjim]

I sense over tightened cam chain as the whining began after you re-adjusted the chain for the second time. Popping and dropping of left cylinder slide diaphram. If it doesn't have a in hole it probably isn't seaated correctlin in the top grove causing a vacuum bypass. I fixed the same issue by carefully instaling the cap on old diaphrams. New ones drop right n the grove no problem. You can get the JDM diaphram kits pretty cheap.

 

[Ludlow]

Thanks for the pointers guys. I'll check that sump oil screen Saturday. If the diaphram isn't seated properly I'm gonna kick myself for spending way too much time on the wrong end of the carbs. I never thought I would hope for a hole in the diaphram - at least I could blame something other than me. Damn my pride.

The cam chain retension was done warm, not cold or hot. The whinning was there before and after, so maybe I had already lost the plastic. I read plenty about the tensioner before posting but I couldn't find anything about the high pitch whinning noise. I've got my fingers crossed going in, better a cam chain tensioner than cam bearings. I'll let you guys know what I find.

Thanks!

 

[Ludlow]

Status report - pulling the left carb to check the diaphram, I noticed the clamp between carb and head intake wasn't tight. I must have overlooked after rebuilding the carbs. The diaphram looked great and was seated in it's groove, so hopefully just a loose clamp letting too much air in.

I drained the oil and saw lots of metal (seems like aluminum paste) in the oil. There was a little build up on the drain magnets, but way more when I dropped the filter pan. My filter didn't have the crushed corner I read about, and no plastic bits either. The magnets on the filter had a lot of the metal powder and so did the pan.

I went ahead and pulled the cam chain tensioner, and it looks great. All the plastic still intact and not even worn. I pulled the plugs again and rolled the engine over. Still feels chunky. I put my finger in the cam chain tensioner opening while turning. The back half of the chain occasionally tensioned while I turned. Is this normal? I'm turning counter clockwise, correct rotational direction. I didn't expect the cam chain to come back toward my finger. Maybe valve spring tension pushing back? I'll be sure to check cam timing after turning without the tensioner, can't be sure I didn't skip a tooth.

Anyway, I'm staged to pull the motor and start disassembling. Sure wish I would have known this while waiting for the paint job... Hey - I got to ride three days so far this summer

 

[addison]

Good luck with the tear down , I cant tell you if it's normal regarding your chain. Dont forget to check the cam chain guide thats where if found the trouble on mine .Let us know how you make out.
peace

 

[Ludlow]

OK, here's where I'm at. I pulled the cam cover and can't see if the bearings are toast or not. With the rockers off, the engine turns over by hand a little better than before. There is some resistance but it's probably the rings in the cylinders. I put a little oil down the spark plug holes, and it smoothed a little more. To do this right, I should break the cam chain and spin the cam bearings to be sure. There just doesn't seem to be any indication that they are bad. No axial movement and not a sound from them while turning by hand.

I'm beginning to think the cam tensioner again. I noticed the vibration dampner on the front side of the engine. Is there a way to check this without pulling the head?

I'm finding myself at the fork in the road. If I break the cam chain, I might as well tear down the whole engine for inspection/renewal. If I decide that, we'll be done with summer by the time she's road ready again. Compression is great and gear train is tight, no reason to suspect problems. I do have a crack in the case that is JB welded - I should fix that right...

You guys can probably sense my indecision. Any short cuts come to mind? Compelling reasons to continue the tear down?

Thanks.

 

[addison]

you can get at the guide on the front side of the motor without breaking the chain , with the damper out the chain should be slack enough to get the cam to slide out.I used a wire to keep a hold of the chain so it didn't fall in to the motor ,then lift the cylinder head up , the chain should feed down through the middle.Tie the chain off again and from there you can pull the guide and inspect.Note it did take a little help from a screwdriver to get the chain off the cam sprocket to start the process.
I wish i knew more to help you but everything i know about these bikes i learned from this site.
peace

 

[Ludlow]

Thanks for the info. Given the fact that my crank case is cracked, I think I finally convinced myself to make things right. I'm going to continue the tear down and make sure things are OK, since I want my bike be worry free for years.

There's a couple crank cases on ebay right now that could get me going, unless one of you guys could cut me a deal... Numbers don't matter since they already don't match. The title is what really counts.

Thanks to INXS' great photo and explanation, I understand that the case upper and lower halves have to match. We'll see how the prospective seller responds to the question of match marks.

Fortunately, I want this to be correct. Unfortunately, I have too many project that I want to be correct. I think I have enough invested in this bike to see this through. Wish me luck...

Thanks for the support.

 

[Ludlow]

BTW addison, thanks for the pointers. If my cam chain is worn enough to get the cam out, I can continue with the disassembly without having to hassle with breaking and re-crimping it. Seems like a huge time saver to me...

Thanks again!

 

[XSLeo]

Ludlow, you can slide the cam bearings off the cam, then slide it out from under the chain. No need for a screwdriver to pry it off.
If you can pry it off with the bearings in place, I think it's stretched enough to need replacing.

 

[Ludlow]

WOW!! That worked great! Thanks XSLeo, I never thought I could do that. I guess I figured the bearings were pressed on the shaft. That beats the heck out of breaking and re-crimping the chain.

Why did they use 2 single row ball bearings instead of a double row configuration?

 

[XSLeo]

I remember reading about that. If I recall right, Two thin bearings carry the load better than a double bearing.
Two singles are probably cheaper than one double row bearing.