Top End Noob

[mike_of_bbg]

Don't see why you couldn't. You won't have to worry about holding the throttle open You'll also be drawing in un-filtered air, but just for a quick compression test that should be NBD.

[MisterCinders]

Hurm, I didn't consider the filter issue. Perhaps this is too clever by half.

Oh well.

[MisterCinders]

Big shout out to Nessism who came through like a champ with a replacement bearing cap bolt! All should worship the ground he walks on.

Over the weekend, I double-checked one of the valve assemblies to make sure it was seating well, reinstalled the cylinder head, tapped out the exhaust bolt holes and got the exhaust back on there. I might need to do a hair more tapping on one of the bolt holes, but I think the pipes are solidly on there. Not trying to tempt fate on another bolt fiasco.

With my shiny new bolt, I can finally time the chain, install the camshafts, install the tensioner, and check the new valve clearances. God willing, I may get to test compression and even start the damn thing.

[MisterCinders]

So I installed the camshafts, idler and tensioner and set the timing. When I hand turned the engine to confirm the settings, I found some slack in the chain that jumped a tooth. No problem, just had to redo all the timing stuff.

*side question - Do you have to install the idler before turning the engine? Can you turn it a few times to check things and then install that piece? I installed it both times before hand cranking because Clymer sets it out in that sequence, but it would be nice to postpone that part of the process to save a step and facilitate double checking the pin count between #2 and #3.

Anyway, the second effort came in nice and tight. Checked and adjusted valve clearances. A couple of them were tight, a couple were pretty loose, but it looks like the valves are closing well (they did not seep any acetone when tested).

Did a compression test. The results were much better, but still a little wonky. A cold test came up with 90/90/65/90. The 90s don't trouble me, since I expect those to come up once the new rings break in. The off-kilter compression in No. 3 is troubling. Those valves and rings should be tight. That is the cylinder that had the bad spark plug hole and previously botched insert (one of the f**kups that wasn't mine). I retapped and installed a new insert there. I know that inserts are bad, etc. But the insert is the only candidate I can think of as the source of bad compression. The compression tester is pretty hard to insert into that deep plug hole with mildly sketchy threading. In fact, before the tear down, the bad plug hole prevented any compression testing. So I may not be getting an ideal connection with the tester, and/or the insert may not be sealing well. I have a replacement head coming anyway. If I cannot sort out the compression issue, I may just swap out the heads later, provided that the various threads on the second head are legit.

Next, I ghetto timed the ignition (using the grounded exposed spark plug to time the spark). I cannot seem to find a good connection for my static light.

Installed the carbs -- which have been completely rebuilt, dipped, re-jetted, exorcised of demons, etc. Set the fuel screws 1 turn out and the air screws 1.5 turns out to start.

Ran some petrol into it. Checked for float bowl leaks, so far so good.

Hit the starter. Turned over, but didn't catch. Curses.

Installed the spark plugs . Heh.

Grabbed a fire extinguisher, just in case.

Turned on choke.

Turned key.

Pushed starter button.

She fired right up like a dream. WOOT!!

Of course, there are still more tasks on my list before riding this beast. I need to vacuum synch the carbs and fine tune the fuel and air mixture. Before I get to that, however, I have a couple of snags.

1. Tachometer. I reconnected the tachometer when I installed the head, but I botched it somehow. Specifically, I get no tach readings on the dial. I must not have properly connected the cable to the worm gear. Because the pipes were hot from idling, I left it until tonight. Hopefully, it's just a simple connection issue, since I need a tach to set the carbs, idle, etc.

2. Smoke. I only ran the engine for 2 -3 very short periods, less than a minute each time. After 10-15 seconds, there was some light wispy smoke coming off the head and the header pipes. I killed the engine each time it appeared. My best guess is that various drips, drabs and my greasy paw prints are burning off as the engine warms. There is nice light smoke (not black or white, etc.) coming from the tailpipe, so I don't think the pipes are clogged. The head smoke did not seem to come from any particular source like a bad pipe connection. The gasket seams also don't show any drips or leaks so far. Tonight, I will wipe down and clean off all the surfaces to eliminate any grime that might be burning off. Hopefully that is all there is to it.

[MisterCinders]

Crap.

Looking at the service manual, it says to remove the tach drive gear when disassembling the head. I only disconnected the tach drive cable, because I am dumb.

I have not heard any grinding or other scary noises from the head, so hopefully the worm gears did not shred. Guess I will try hand-cranking to see if the tach spins or not, and remove the tach gear to inspect for damage, reinstall correctly, etc.

I swear Clymer (whom I trust less and less) only said to remove the tach cable. Ugh.

[MisterCinders]

OK - the tach issue was very simple. Way back when I disconnected the tach cable, the actual cable slithered right out of the tube. Once I remembered that and snaked it back in, the tach works fine.

I suspect that is NOT how it is supposed to be, but I can work with the results for now.

Still getting some smoke when it idles, but it looks like its stuff burning off the pipes, especially underneath where the 4 header pipes join into the one tail pipe. I continue to scour for leaks to make sure that it is only old grime and not fresh oil drips from a leak.

Now I have to revisit the idle and mixture puzzles with these carbs. So far it seems to need choke to run, but the smoke investigation deters me from running the bike very long. The idle also wanders a bit, sometimes struggling to hold rpms unless I adjust the idle screw, but then creeping up too high.

I need to continue to fiddle with that to get her idling steadily, so I can set the fuel/air screws and synch.

[Nessism]

Did you replace the intake boot O-rings yet? If not, you need to otherwise you can get vacuum leaks.

One other thing you should do is torque the cylinder head again after you put a few heat cycles on the engine. Do NOT skip this step otherwise you can get leaks. Also, check the valve clearances again.

[MisterCinders]

Follow up question.

I understand that cold compression numbers tend to be low, and that new rings and jug hones will take time to settle in before compression will increase after use.

How long in terms of miles/running time before I should expect to see better compression results?

I just got a replacement head that may not be necessary if this rebuild settles into place. OTOH, if that No. 3 cylinder continues to show bad compression, it has to be that bad spark plug hole, since I have rebuilt/replace everything else. So I can clean up this second head and do another teardown, if I have to. I prefer to stick with the current build if possible, though.

[MisterCinders]

Did you replace the intake boot O-rings yet? If not, you need to otherwise you can get vacuum leaks.

One other thing you should do is torque the cylinder head again after you put a few heat cycles on the engine. Do NOT skip this step otherwise you can get leaks. Also, check the valve clearances again.

Yes, I replaced the intake boot o-rings and fasteners with fresh rubber and SS allen-heads from cycle o-rings. I also replaced all the carb o-rings with a set from Barr. Just in case, I have a full set of new carb rubber from Barr as a back up.

Thanks for the follow-up torque advice. I checked and adjusted the valve clearances when I put her back together. If I cannot get the idle sorted, I can go back to those valve clearances. Between my old spares, some club shims and the parts on this new head, I am swimming in shims. Once the thing is running, I will hook the club up with plenty.

[mike_of_bbg]

I'd say after 2-300 miles you should see your numbers improve. Maybe not even that long. Don't baby it!

Repairing spark plug threads has been done before with the head in place. There's advice there about controlling debris from the drilling. Try some forum searches.

[MisterCinders]

I'd say after 2-300 miles you should see your numbers improve. Maybe not even that long. Don't baby it!

Repairing spark plug threads has been done before with the head in place. There's advice there about controlling debris from the drilling. Try some forum searches.

I already repaired those threads, but the lower compression in that cylinder relative to the others makes me think that repair might be losing compression, leaky, etc.

[MisterCinders]

Yowsa! That new head came in and it looks pretty sweet. The valves and seats are in great shape, just need to clean off some carbon. Dropped the valves into some Berryman's and am very tempted to go ahead and swap heads.

Did some more fiddling with the idle. It is running, but not great. Plugs looked a little sooty, so I backed out the air screws a little. That helped some.

My chief concern on the idle so far is that the No. 3 exhaust header is much cooler than the others. Not ice cold, so I think it is firing. But it only feels warm, not yank your hand away hot like the other three pipes. The exhaust also is backfiring/popping at the tail pipe. Will continue to fiddle.

[Nessism]

Sounds like #3 isn't firing. I'd check for spark first.

[MisterCinders]

OK that No. 3 cylinder is possessed. Checked the plug grounded against the frame, and it's getting spark. The float bowl has fuel. But that pipe is cold.

New compression test shows improvement, but No. 3 is still out of step. 120/120/90/120

So fuel, spark and some compression but No. 3 gives me the bird. What the hell?

[MisterCinders]

I have an odd theory on the No. 3 cylinder. Tell me if this makes sense.

Recall that I have spark, low but enough compression and fuel flow, but no firing on that cylinder.

When I pull the No. 3 and plug and ground it against the engine, it sparks fine. Also, the No. 2 cylinder is running, so the coils and ignition are not the problem. After beating my head against a wall, the spark plug insert came to mind. The instructions for the plug insert said to use blue loctite to secure the new threads, so I did. Is it possible that the loctite is causing the plug to not ground well? Is loctite conductive? If I used too much of the stuff, or should not have use it at all, could this be blocking that cylinder from getting a good spark?

If this theory craps out, then I am out of ideas. OTOH, if the loctite is the villain, I already have a head to swap out (and it looks better than my original so far), so I can commit to that as a fix.