Timing? Valves? Both? Or other? I need help.

I have a 1982 xj650rj.

It's running and, most recently, driving (I've driven it down the street and back a couple times). It's pretty solid. However; I've read a lot of manuals and searched through too many threads and forums and I can't seem to make any sense of how to solve these issues...

1) once started with a little starter fluid, I have to hold the throttle all the way open for it to idle. If I release it the bike dies.

2) when the bike gets warmer I can drive it, but the rpms have to pretty high or it loses power and slowly dies. (I don't have a working tachometer, so I am unable to tell you what the exact rpms are)

3) I have low compression in all cylinders.
#1: 65 psi.
#2: 85 psi.
#3: 88 psi.
#4: 90 psi.
*After putting a little oil in all of the cylinders compression shot up:
#1: 87 psi.
#2: 100 psi.
#3: 110 psi.
#4: 110 psi.
But that's still too low. That was my first compression test and I've heard that holding the throttle open would change those numbers, but that's still all over the place. Compression going up after oil suggests that rings are bad.

4) after riding I checked the spark plugs. This is them.

Clean on 1 and 4, and a little oily on 2 and 3. I also decided to feel the exhaust headers (because I read something about header temps); 1 and 4 were warm enough to keep my hand on. 2 and 3 almost put me in a coma with how hot they were (bad idea to touch headers with bare hands in case anybody needs help understanding that).


5) there is an air bubble in the inline fuel filter and the filter normally becomes empty of gas after I pull the throttle, leading us to beleive that it could be starving for fuel as well...



*I have taken the carbs to church. They are immaculate. They do need to be synched and adjusted to be at top performance, but I'm pretty sure that needs to happen later*

I was told to check the valve clearances to see if that could be a problem for such low compression as well and I found that all of the clearances were off by a lot. On three of the valves I couldn't even fit the smallest feeler gauge that I have (.002" or .05 mm) while some were too large. I have read that engine power can decrease when clearances are too large. These were my results (n/a are valves that were too small to measure).

#1 intake: n/a
#1 exhaust: .005" or .127 mm

#2 intake: .008" or .2032 mm
#2 exhaust: n/a

#3 intake: .008" or .2032mm
#3 exhaust: n/a

#4 intake: .008" or .2032 mm
#4 exhaust: .003" or .0762 mm

Required specs are:
Intake: 0.11-0.15 mm (0.004"-0.006")
Exhaust: 0.16-0.20 mm (0.006"-0.008")

I also found that the timing dots on the camshafts were off when in alignment with the "T" on the timing plate. And, for the cherry on top, the PO stripped the 19mm square fitting to turn the timing plate. I was told that he went through the engine but I have no idea what he did, so I am most likely dealing with his problems.



So....

Question #1: does timing affect valve clearance on these bikes?
If so, how do I know if the timing plate or camshaft timing dots are really in synch with each other after the PO went through the engine before I got it, and what would I need to do to get it back into correct timing?

Question #2: could this be an issue completely separate from timing and/or valves? The bike only has 3141 miles on it. I'm trying hard to believe that this is an issue with the PO's reassembly, but if it's not and you have others ideas please let me know.

I know that's a lot of information to consume at once, but I thought it would be more beneficial to give as much info as possible.

Thank you for your help!

 

T mark is for dot alignment so it looks like it’s off one tooth. the valve clearance will affect compression test as well.
C mark is for setting cam chain tensioner if you have a manual one.
Get that sorted first.

Compression test all plugs out.
Air filter out.
Throttle wide open.
Crank for about 5 seconds.

 

Is there a reason the cam shaft bearing caps are loosened and it looks like the one just out of the picture is removed? I wouldn't be messing with those at all unless absolutely necessary. My (vague) understanding is the sleeves, shims, however the bearing clearance is set is done at the factory in a semi-custom way per engine, so if you swap anything around you'll be in trouble without doing that same tolerance setting...

 

No reason other than to check wear.

 

Cam swaps can normally be done without issue. Yamaha was kind enough to grind all of the cam bearing journals to the same size, and line-bore all of the cam bearings to the same size. Test-fit with plastiguage to be sure that the clearances are within spec, but it's typical for everything to be fine.

I agree that the cam timing is off by one tooth on both cams (that may have been intentional, but it's not by the book).
The C mark is also for replacing the automatic chain tensioner when it's been removed for adjusting/ replacing the cam chain, or removing the cams for any reason.
Your cam chain is a replacement, and it's likely that is when the cam timing was set a tooth off.

Cam timing does not affect the valve clearance, but does affect the timing of the opening and closing of the valves (clearance is checked with the nose of the cam pointing 180º away from the shim face, regardless of what the cam timing is set to). Correcting the cam timing is as simple as removing the camchain tensioner, removing one cam sprocket, and moving the chain accordingly).


#1 ad #4 definately have oil on them, and that is of some concern.
#2 and #3 are both lean, but not too far from being on the money.

As for the oil and low compression: how long did the bike sit, and do you know if the PO had done any work to the cyliners (maybe a rehone and new rings was done)?

 

Thank you for simplifying that for me. I bought the bike about a year ago, so I'm not exactly sure how long he said it sat, but I remember it was a few years. Maybe 2-3. From what I remember, most of what he did to the motor was replacing gaskets, but I can't be sure of axactly what he did to it and that kind of scares me.

 

Im not an expert but it looks like to me that the timing indicator has been moved from factory setting.

 

The small metal piece used to line up the "T" and "C" with?

 

Yes....it DOES look a bit weird....slotted?, I've not had my timing cover off for quite a while, but I would check it not been loosened/moved...or even 'slotted' just in case, unless someone tells you it's supposed to be like that #factory...

 

There should be a spot of paint on that screw head. If it is cracked or gone its been messed with.

 

Nice catch Dude... made me want to go look at mine.

Yes the one in the pic above looks messed with, here's mine

 

Paint spot looks good to me.

 

yes, I meant his does not...

 

My bad, your paint spot looks good.

 

*update*

I aligned the "t" at TDC on cylinder #1, adjusted the stationary pointer to match, and adjusted the cams.

This is the progress:





Will this be close enough, or is there more adjustment needed?

What do you guys think?

Thank you!

 

I usually just use a pencil in the #1 plug hole to find TCD. It's an old habit.

 

Sorry, that's actually how I determined tdc..
You're right, it works really well!

 

**update**

I got the timing as close as possible, cleaned the old gasket off the cylinder head, and I will be cleaning the valve cover gasket side later tomorrow.




Thanks for all the comments!

 

Looks right up top

 

Yep. You got that dead on.

 

So, if the mark on the pencil from plug hole #1 at TDC doesn't match the mark on the pencil from plug hole #4, turn the square nut on the
pickup plate to make the marks on the pencil the same then shift the indicator to line up with the TDC mark ?

 

What I did to determine accurate timing was find TDC on cylinder #1, unhooked both sprockets on both cams, turned both cams until their timing dots (small black dots on top of each can) we're lined up with the appropriate tick mark (on the cam journals), and then I adjusted the stationary marker to line up with the "T" on the pickup plate. From what I have read, timing is first determined by TDC in cylinder #1 and that's it. If I am wrong then I'm sure someone will correct me.

Good luck!

 

your crank is bent

 

This was a great series of pictures. They explained how timing works, perfectly. My Question now is, in installing the intake cam shaft , the pistons
#1+#4 are up, So the cam lobes for #1+#4 would point up, but pistons #2+#3 are down so the cam loves would point down. Since those valve springs
are not compressed one would have to push down on the cam lobes of #2+#3 in order to get the bearing caps on. I thought of using a clamp on a bearing cap
to get the cam into place. Is there a better way ?

 

pull down the cam evenly with the bearings, then roll it around to get the marks lined up. notice the hex cast into the cam near the middle.
if you use a clamp in one place, you run the risk of bending or breaking the cam

 

so the cam bearing cap bolts are long enough to screw the bearing caps down and push the lobes down over intake valves #2 +#3 ?

 

if you turn the crank 90 deg, the pistons are at mid stroke now the cam can spin anywhere it needs to be, to get bolted down

 

Got your metters lixed up....

 

What are you talking about hogfiddles ?

 

I wrote Top Center, Dead. Perfectly fine military nomenclature

 

So now I have bolted down the intake cam at 90 degrees off of TDC. Next comes the exhaust cam. Do I leave the crank shaft in the same place ?
Or rotate it to another position. Do I hook the chain onto the intake sprocket first, or wait until I have both cams in place ?

 

that's as good a place as any.

i think i see what your trying to do, i don't think it works.
put the ex cam in, unbolt the sprockets, put #1 at TDC, put the cams on their marks, jump the chain on the sprocket until their bolt holes line up with the cams, the cam marks won't line up perfectly but if you go one link either way you'll see them go way off.
when you bolt the cam down, make sure the chain goes around the outside of the cam..... i done did that once
sprocket bolts are tight, put them back that way, use thread locker

any more tips out there?