Topic: valve timing cb400f 1975

[Redline it]

would it run at all if the cam/chain/crankshaft were off by 1 tooth? or would valves come in contact with pistons? either one.?
the reason for asking is from never removing the chain from the cam, it was put back together, i did loosen the tensioner adjusting bolt and the the crankshaft/camshaft wasn't at any special set point. and the horseshoe moved quite a bit, i think while the rear slipper hold down mount was loose as well)and since then the valve clearance was checked around the 8 valves and then checked again making a couple of adjustments. put it back together and got it to run briefly before shutting it off 2 times to see if oil pressure was reaching the top, and still wasn't quite sure but after running the crankshaft with a drill i could see oil dripping off the valve rocker shafts. now checking valve timing it's like everything has changed with no  clearance at all on the exhaust sides with t mark lining up with the reference mark. oh and tricky to get the gauges in from the angles, it was more tricky than ever lighting is terrible where i'm at. it's usually a 30 min job and now' it's a monthlong.

[M 750K6]

When i stripped its head, my 750 was off by one tooth of the cam chain sprocket. IIRC, the valves would have been too early.

Although i had never ridden it properly timed, it ran fine, I had other problems (leak) which prompted the strip down. There were no signs of valve contact with pistons.

The no clearance point, did you originally set valve clearances after setting the cam chain tension? No experience with 400s, but personally, with the valve cover on, because of the access angle, I find the 750 is a bit tricky getting feeler guages in and judging the level of play when you slide the feelers. Would be easy to misjudge.

[Tim2005]

Someone on here a couple of years ago rebuilt a 400 and it would run but wouldn't rev above 4000ish, it turned out they had got the cam out by 1 tooth. Though I cannot remember if they had it 1 tooth advanced or retarded, and that would probably make a difference too

[Little_Phil]

I put this down to one tooth out on a 500, but can't be sure.

[Redline it]

When i stripped its head, my 750 was off by one tooth of the cam chain sprocket. IIRC, the valves would have been too early.

Although i had never ridden it properly timed, it ran fine, I had other problems (leak) which prompted the strip down. There were no signs of valve contact with pistons.

The no clearance point, did you originally set valve clearances after setting the cam chain tension? No experience with 400s, but personally, with the valve cover on, because of the access angle, I find the 750 is a bit tricky getting feeler guages in and judging the level of play when you slide the feelers. Would be easy to misjudge.

to the no clearance point, yes i did adj/set them 2 times after loosening the adj push rod, the chain looked pretty loose until the horseshoe moved out so much, and i could push the rear cam chain guide slipper down and the push bar was responding so i was stoked about that, but i left the chain alone, i was having trouble more than ever getting them right, so i thought, by any way by trial and error of loosening the lock nut and sliding the feeler under it and turning the adj screw to lightly contact and then trying to since the locknut by holding and not holding the adj would either immediately get so tight the gauge wouldn't slide or when i got the clearance perfect then cinching the screw would get snug and still have the clearance so then slightly tightening them again the reading would accept a .006 or .007 but i finally get them where i thought was good.  last night i got 1/4 done by watching the intake valve go all the way open and after it started to close i'd watch the  plate for 1/4 to show up on the T line. and got 1 done, turned the cs over 360' to 1/4 and adjusted #4 and put the caps on those, if they aren't right it might be trouble for the bike. so watching today #2 intake valve fully open and on its way to close i look at the points plate and it's on 1/4 nearly exactly where it shows up on the 1 and 4 valves.  so do i just keep on turning the cs until 2/3 shows up, it's like 180' more isn't it? i've adj these 400fs for 40 years with no problem like this one is giving me. plus never watched the intake valves in the procedure before. but have changed head and base gaskets it took a couple tries and it's been holding now for a few years.  and of course there's also minor things i do that also are becoming really difficult, but the brain fading and the 400f troubles aren't related that i can see. if they are, then i'm getting a front row seat on how much fun old age is gonna be.

[Redline it]

Someone on here a couple of years ago rebuilt a 400 and it would run but wouldn't rev above 4000ish, it turned out they had got the cam out by 1 tooth. Though I cannot remember if they had it 1 tooth advanced or retarded, and that would probably make a difference too

that's what i'm fearing might of happened. so i hear the cam cover can be removed with engine in place and to correct that if it is the problem is the fix taking the cam gear bolts out and moving the chain over a tooth?

[Tim2005]

Yes that's all you'd need to do. Just be careful not to drop the cam bolts down the tunnel...

[Redline it]

Yes that's all you'd need to do. Just be careful not to drop the cam bolts down the tunnel...

after the cam sprocket bolts are out, do I have to reset the tensioner horse shoe by loosening the cinch bolt and pushing down on the rear slipper or do I have to loosen the cinch bolt and the push rod cap and then push on the unbolted rear slipper as much as I can before tightening the cinch bolt and the pushrod cap in that order. Just with the valve cover of how can the valves be checked for being bent, would it be noticable from the top by a spring or valve stem being slightly off from the other valves, I was hoping to avoid removing  the exhaust or carbs to see if light escapes out of there

[Redline it]

Looking in the spark plug hole for light shining on top of the valves, cam cover off will show light if valves aren't sealing, or at least if they're far from sealing. I'm guessing. I took the cover off it looks good, as it did before putting it on, The 2 dowels were in place, only the oil trays weren't as full as I thought they'd be, both were equal and high enough that the cam journals and rocker lobes were all in the oil. All I gotta digure is if I got to reset the can adjuster after finding out which tooth skipped(if it did) and move the chain in the right direction. The odometer shows 10500, so chain is probably not stretched, if any thing slipper guides could be if it was over tightened and ran that way.

[Redline it]

here's the latest: with rocker cover off, rotating the engine so that cam lobes on #1 cylinder are both intake and exhaust are pointing up (obviously  on compression stroke) the#4 they are both down, the right side of the cam has a hole drilled into the cam that looks to be straight up.looking in that position looking at the point plate in the hole it is 1/4 F lining up with the case mark. so does that look like it is off a tooth on the cam? i'm guessing that it's as close tor right as it can be. maybe some timing experts here can confirm that?

[Tim2005]

Do you mean 1/4 F ? TDC is 1/4 T. F is the mark  for the ignition. Could this be the problem I wonder...

[Redline it]

tim i just read that in an old post. so it's at the F mark, i'll turn it around again and i'll stop the crank, wait the T mark is next in order but a small move from F mark, i checked it out and moved the cs to the Tmark and the lines on the cam gear are lined up exactly matching the case. so that's good news?

[Mark1976]

The orientation of the camshaft with the #1 piston at tdc. Leave the camchain adjuster alone until after its back together.....   

[Redline it]

The orientation of the camshaft with the #1 piston at tdc. Leave the camchain adjuster alone until after its back together.....

ok thanks, i'll spend the evening putting it back together, the reason i removed the valve cover was adjusting the valves according to a factory underseat manual for the 75 400f that it is. and then after 1 and 4 valve lash adjustments, rotated the cs until the #2 intake valve opened up and just as it starts to close, i watched the plate hoping to find the T mark on cylinders 2/3, but it was at 1/4 with the cam in what i thought was 2/3. that lead to a belief of cam chain a tooth off. these boards could use an update in how suggestions are given, with one locked on to do that work and then get paid directly a tip or a based price.

[Redline it]

Do you mean 1/4 F ? TDC is 1/4 T. F is the mark  for the ignition. Could this be the problem I wonder...

i don't think so. i didn't stop at 1/4F for any reason. i wasn't even looking at the line on the crank gear until i moved it to the /4 T mark. but now that it is looking like it's in the right assembly position. i guess i'm putting it back together. nothing to do with the slipper etc, i checked the oil out put by kicking the motor over a few kicks and oil was flowing out the little spray bar. so it wasn't a big waste of time also i double confirmed that the 2 dowels are in place.  mark1976 says not to do anything with the tensioner until it's back together, i do want to find out why. that might explain what happened last time it was open, i did that. and i don't know what that did. all i seen was when loosened the lock bolt i was looking down the rear or in between both front and back timing chain to see if the tensioner was seized. and it sprung out. so i removed the rear slider mount and to push it back and forth against the spring only but pushing the slider back down so i could put the cap back on it. i had the feeling that was a stupid time to look at its action. i didn't even load one side of the sprocket like slack in the front or rear. i appreciate your picking this up. the manuals are pretty vague on things. like the tensioner.

[Redline it]

The orientation of the camshaft with the #1 piston at tdc. Leave the camchain adjuster alone until after its back together.....

is that picture with the cam lobes down i never noticed the dotted bolt heads, if that's what i think it is, it's looking at the cam from the No. 1 cyl side, if so that could be my problem because i always thought it was looking from the right side or from the No.4 cyl. that leaves No. 1 lobes looking up, but there's slack on no.1's in and ex at that point. i'm 180 or 360 off aren't I.

[Mark1976]

Step 1.  #1 piston at tdc,
Step 2.   Hold the cam sprocket and chain together, side by side
Step 3.   Install the cam by sliding it thru sprocket and chain in the orientation shown
Step 4.   Put the cam chain on the cam sprocket and then pull the sprocket onto the camshaft in the orientation shown
Step  5.  Install and torque cam sprocket bolts (2)
Step  6.  Verify cam and sprocket orientation
Step 7.   Install cover and torque it down, carefully, avoid rockershaft valve tip binding.

                FULL STOP.
Once the topend is assembled you can adjust valve clearance's and then the cam chain tension.

[Redline it]

Step 1.  #1 piston at tdc,
Step 2.   Hold the cam sprocket and chain together, side by side
Step 3.   Install the cam by sliding it thru sprocket and chain in the orientation shown
Step 4.   Put the cam chain on the cam sprocket and then pull the sprocket onto the camshaft in the orientation shown
Step  5.  Install and torque cam sprocket bolts (2)
Step  6.  Verify cam and sprocket orientation
Step 7.   Install cover and torque it down, carefully, avoid rockershaft valve tip binding.

                FULL STOP.
Once the topend is assembled you can adjust valve clearance's and then the cam chain tension.

10/4 on that and thank you very much. all this seemingly problems i'm having i believe i was adjusting valve clearence at bdc on #1/4 and for some reason i was able to put it back together with 2/3 also set wrong, but it worked and ran for a brief time 2 or 3 times, no snaping or banging nor any sounds like something was in the way. is that even possible? Any way i'm gonna try to start at tdc #1/4, just looking at the cam  and the next in order is 1-4-3-2, so it's gotta be close to right. takes a full day to torque the head bolts, i add at least 2 stages before the start of what the manual says to, like 3 stages, that way i know i'm not way off on over torquing 1 or forgetting it all together until it's done, and even the head bolts with threads in them to finish out the cover bolts i include them and torque them the same as the others get. it's nerve wracking but it's what i do. i never have loosened the cam gear yet.

[Tim2005]

Sounds like you've got everything covered now. In any event it was useful to check you've got good oil flow from the spray bar

[jonda500]

Some more points that may help:

The firing order is 1243, not 1342 like most 4 cyl, car engines.

When the cam lobes for #1 are both pointing upwards #4 is on compression and vica versa (spark fires both 1 and 4 every time crankshaft passes the 1/4 F mark).

For orientating the sprocket correctly only lining up the 1/4 T mark (top dead centre) matters - it doesn't matter if the #1/#4 lobes are pointing up or down (because it fires both 1 and 4 together every time).

You cannot cause any problems by messing with the tensioner before replacing the cyl head cover or before adjusting the valve clearances, however the correct procedure for setting the tension requires the cover on and clearances set.

To find #1 compression watch #4's tappets closely while turning the engine forward slowly - when the exhaust one is nearly back up(closed) just as the inlet one starts to go down(open) turn the engine back and forth slightly until the 1/4 T lines up and you have #1 ready to set clearances. (If the adjusters have been backed out you will first need to wind #4 adjusters both back in to approximately where they were.)
John