1981 KZ750 LTD four questions

Scirocco wrote:

The engine sounds good and need only a good carb sync.
Sounds like three cyl. pushing/pulling the one cooler cyl. in question.

 

Yep so carb sync was on the list of things to do already, and I've got gauges, possibly not the best quality but they weren't the cheapest option, if they seem unreliable they'll be going back. 

What do you mean by your second sentence?

The throttle butterfly gap of the cooler cyl. is a little bit more closed, so this cyl. do generate less power output and do more drag.

Alright so what feels like forever later, I am electing to delay the gratification of just riding the damn bike, and doing some due diligence. Today I pulled the valve cover and checked all 8 valves, twice with the FSM method and twice with the method Nessism has posted here, and on several other posts. My results were... uninspiring.

FSM Method Results
1I 0.15; 0.15 1E: 0.10; 0.12
2I 0.13; 0.13 2E: 0.08; 0.09
3I 0.13; 0.13 3E 0.13; 0.14
4I 0.13; 0.13 4E 0.13; 0.13

"The Other Way"
1I 0.08; 0.10 1E 0.06; 0.08
2I 0.08; 0.08 2E 0.06; 0.08
3I 0.13; 0.13 3E 0.10; 0.13
4I 0.13; 0.13 4E 0.08; 0.12

So 3 and 4 were relatively consistent across both methods, and 1 and 2 were all over the damn place. Do I just suck at measuring? Brand new set of feeler gauges, since apparently I lost mine in the most recent move... Also @Nessism in your prefered method, the last step has you index the #4 exhaust to measure the 3/4 intakes... I'm assuming that is a typo?

Anyone have any ideas? I was feeling good for about a quarter of a second and was ready to order some shims for 2E, but now I'm having second (and third) guesses. Did I need to do anything with the cam chain tensioner before taking off the cover? Could that be throwing things off? I assumed you'd want everything taught to turn the engine over for the clearance checks... 

Unrelated (except it also happened to be today) I learned some dillhole must have stripped the oil drain plug and tapped it out to 7/16"... 

bluejacobs wrote:

. Also @Nessism in your prefered method, the last step has you index the #4 exhaust to measure the 3/4 intakes... I'm assuming that is a typo?


 

Yes, a typo.  So sorry.  I asked a mod to fix.  I don't want anyone to follow this incorrect instruction.

Nessism wrote:

bluejacobs wrote:

. Also @Nessism in your prefered method, the last step has you index the #4 exhaust to measure the 3/4 intakes... I'm assuming that is a typo?


 

Yes, a typo.  So sorry.  I asked a mod to fix.  I don't want anyone to follow this incorrect instruction.

Done

Not to worry - I figured it was an honest mistake and indexed #4 intake to measure I3/4... going out to the garage again shortly this morning to take another round of better rested measurements... I know the cam chain tensioner will need to be removed before I put the cover back on at the end of all this, but I didn't mess up by not removing it before starting did I? I've also seen references to "locking" it before starting? Would that make any difference??

bluejacobs wrote:

Not to worry - I figured it was an honest mistake and indexed #4 intake to measure I3/4... going out to the garage again shortly this morning to take another round of better rested measurements... I know the cam chain tensioner will need to be removed before I put the cover back on at the end of all this, but I didn't mess up by not removing it before starting did I? I've also seen references to "locking" it before starting? Would that make any difference??

Leave the cam chain tensioner active during your checks, that way you won't jump time.  Sounds like you are doing a good job.

So again, the method I recommend was adopted on the 1000 & 1100 sometime near J model.  And it's same as Suzuki GS bikes used.  It places two adjacent cam lobes on the base circle at the same time, which eliminates skewing the cam in the journal clearance from the adjacent valve spring pushing the cam up.

Alright so I did one more round of measurements this morning using each method and they were pretty much right in line with what I came up with yesterday. 

FSM Intakes 1-4: 0.15; 0.13; 0.13; 0.13
FSM Exhaust 1-4: 0.10; 0.08; 0.15; 0.13

Alt method Intakes: 0.08; 0.08; 0.12; 0.12
Alt method Exhaust: 0.08; 0.06; 0.13; 0.10

Biggest and most concerning discrepancy is between Intakes 1/2 between methods, highlighted red. What could possibly cause that, when most all the others the ALT method was around 0.02mm tighter???

Looks like most everything could be opened up by one shim size (0.05mm) , and still be in spec regardless of methodology but at the very least, Ex 1/2 could do with a little more clearance. Thoughts?

On the face of it (just my opinion) but that much difference only on the two adjacent lobes for #1 & #2 where the only significant difference between the methods is valve spring loading on one of the lobes would possibly suggest worn cam bearings in that cap ??? (I can't see where else that movement can come from ??)

Got my hands on some red plastigage, got to TDC, took out the tensioner, popped the intake cam loose cleaned up the surface of the cam and each cap respectively and placed a piece of plastigage on each... torqued following the FSM order and opened everything back up... got approximately 0.102mm clearance on #1, and approximately 0.076mm clearance on #2... so both in spec. Pulled all four caps and they all looked roughly the same wear wise, and felt smooth despite some non-uniform coloration on the cap sides... Cleaned off the plastigage residue, put everything back together, reinstalled tensioner, retorqued everything, and remeasured valve clearances on Intake 1-4 ... Intake 1 and 2 snugged up .02 or .03 mm each with both methods.... Stumped.

Also I couldnt really tell if there is a separate piece fit into the cap that is a "bearing" or if its just part of the cap itself? What am I looking at/for - I didn't see "cam bearings" anywhere on parts diagrams as a serviceable item... 

I may just look at my pairs of measurements and if sizing up the shim 0.05 would bring the smaller Alt measurement into spec, but wouldn't push the FSM measurement beyond 0.18, I may go that route and call it good... RE: Alt: 0.05 FSM: 0.13 + 0.05 yields 0.10 / 0.18 .... thoughts on this approach? Seems haphazard and like guessing... 

It's normal for the "alternate" method to show less clearance, because the cam isn't skewed in the journal clearance.  It's sitting more central.  When I performed this same trial on my bike, I was seeing a difference of .02 - .03 mm difference between the methods.  I can't explain why your bike is showing so much difference.  

My opinion, I'd go down one shim size on #1 & #2, both I and E, and then remeasure.  Be sure to oil everything on assembly, and turn the engine over a few times before measuring.  Worse case, too much clearance, in which case, put the old shims back in.  Possibly a time waster, but a reasonable use of time in my view.

Edit: one other option... Measure clearance with the cam lobe on the base circle, but with the adjacent valve depressed.  This will skew the cam upwards, and increase clearance on the valve you are measuring.  As long as the clearance is towards the upper end of the range, you are okay.  When running, the actual clearance will be less, but not less to the point of being tight.

Getting seriously frustrated with this valve job right now. I'm scrapping the idea of comparing two different methods and sticking with the factory service manual method because I can not cope seeing the differences in the methods and not knowing how to rectify them. I understand 0.02mm difference is expected, but I'm seeing consistently more than that on most of the valves between the two methods. What's more is that I've now had everything apart 3 times to try some fine tuning / shim adjustments and each time, I'm getting DIFFERENT measurements on valves I changed nothing on by a half to a full shim size. HOW. THAT DOESNT MAKE ANY SENSE. How could disassembling and reassembling change those measurements THAT MUCH. Even with the one mistake I made (wrote down 280 instead of 260 for one of the starting shims on I3) when I put in the correct new shim (250) and reassembled everything the measurements on the EXHUAST side had changed... ::SCREAMS IN HOME MECHANIC::