how close is close enough?(cam installation)

So, I intalled the cams as per my manual: Lined up the dots on the boss with the center of bearing caps. Took out the slack on the exaust side and bolted sprocket on. Took out slack between sprockets and bolted intake sprocket. Rotated the crankshaft two turns back to T on the ignition plate (missing a few steps here for brevity). Both dots are just slighty behind (towards the intake) of the center of the caps. Not enought to get a link, but not lined up just the same. Both cams appear to be the same. Is this a slackness issue; i.e., should I do it again and make sure I've got all the slack between the crankshaft and the exaust sprocket? Or is this normal?

I'm done for the night. My initial plan is to give it another go tomorrow evening.

Many thanks in advance.

 

You missed.

There's no room for error. None.

But, you have to be sure you didn't overshoot TDC!

You need to RE-Time the Engine.

That means the Sprockets have got to be OFF the Cams for Exact positioning.

*** There are Several CRITICAL Adjustments Necessary ... You should become Very familiar with the Procedure and do some "Dry Runs" before placing the Cams tight in their Bearing Caps, Pulling-out the Slack, and Setting the Chain over the Sprockets and Re-attaching the Sprockets. The Possibility that the Timing is Incorrect MUST be Tested by rotating the Engine ... slowly, by hand and examining the marks BEFORE Final Torque is applied.
*** Any resistance in the placement of the Cams, Tightening-down, and Test Rotation for determining Correct Timing is cause to Abort, disassemble and re-do the Entire Process.

 

Been through this procedure several times. As Rick says it has to be spot on. However, (there's always a "however")...everytime I lined up the cams and the sprockets etc with the TDC mark on the plate on the side of the engine I could see the indents on the cam through the end retainer cam bridge/bearing. But they weren't "exactly" in dead centre of the hole. They were maybe a a few millimetres out and no matter how many times I jiggled and reset it it was pretty much the same.

Main thing to not is that you followed the Haynes manual procedure RELIGIOUSLY. Checked that it all lines up, checked again, and one more time to make sure.

And then you rotate the engine by hand via the side plate to make sure all valves were activated by the cam in the correct order AND at the right time, just to make sure something wasn't in the wrong place and a valve wouldn't be descending onto a piston (crunch/boing/expensive).

KarlH

 

I've had a slight (and I do mean slight, 1/4 tooth or so) difference between the cam pillow and sprocket marks. It was not in the same direction but, if you follow the step-by-step proceedure in the Haynes, you should be alright (I was/am ok so far). Rick has a very valid point, by performing the task a few times, you can improve the likelyhood of finding a missed step or indication. No harm in redoing it a few times just to be certain (you DON"T want to be off a tooth).

 

Thanks for the tips. I think I'll try again. It probably won't wreak havoc like it is now, but it won't run right. Plus, I'll be more confident with the end result.

Ciao.

 

trust me, just went through this fiasco over the last couple days. I was just a degree off on both cams and i'm lucky the bike is still running. I lined them up manually, put the chain and sprockets back on, spun it twice, and they weren't lined up. Did it all over again and finally got it. The bike now runs great except for the fact it needs fine tuned, but thats for another day.

 

Relatively easy to get it Exact once you've learned how F'ing Yamaha isn't clever (or too damn Cheap) enough to spline the Sprockets onto the Cam shafts like most other DOHC engine designs..have done for 60 years.
The basic problem is that the cam chain guides mess things up by loading the chain so that it moves during setup.
Personally I Do Not remove sprockets.. Ever.. there's absolutely no point as they can only fit one way (no splines)
First set up the Intake cam/sprocket exactly on it's locating mark... then manhandle the Exhaust one into place... After.. making absolutely sure (lock it with a Large Visegrip)) that the intake cam does not move at all.. none.. nada.
This works Try it
Sorry for the inexact description but it's a 'learn by Doing' adventure.

 

Be sure not to lock the cam by placing the vicegrips on a bearing surface or lobe.

 

I'm sure the process gets done the way it got explained there.

ViseGrips are not one of the Tools I'd use near any of those parts, though. No offense.

I get the process. Understand what you are saying ... but, then -- suddenly my mind rejects the idea.

It's like the Subconscious part of my brain's Technical Section begins to glow in a dull, red light and the synthesized voice representing my psyche says:

"I'm - sorry - Rick. I - can't - do - that!"

 

There's a hex section on each cam to let you turn them with an open end wrench for fine adjustment. I was also "close" when assembling my Turbo. It has to be dead on.

 

The one problem with lining everything up is getting the chain back on the sprockets in exactly the right position.

First, the cams are located in their correct positions and the cam bearings/bridges are tightend down - to correct torque level if necessary.

Then a large open ended wrench is used on the hex parts to line them up exactly so that the indents peek through the holes on the ends. The cams are now in their exact correct position.

The trick is, as per Haynes, is to lift the loose unbolted sprockets onto the cam bosses so that the mounting holes line up EXACTLY. Which requires fiddling about with the chain on the sprockets, moving the sprocket off the bosses until the chain is on the sprocket and the sprocket is in the right position to line up with the holes - Jeez Yamaha - couldn't you have made sprockets with some adjustments like an extended oval hole (I've seen them and I believe you can buy them aftermarket). And doing all this in a limited space.

Once the sprockets are mounted, lined up and the bolts have been finger tightened, and the cams haven't moved during the process (where's the Johnny Walker aarrgghh!!!), and the indents can be seen through the holes while the side plate is still lined up with the relevant marks...you're THERE...exactly where you should be, with your mind at rest that the engine is in sync.

Don't get too cocky though - rotate the engine with a spanner via the sideplate over and over until you're absolutely sure it's correct. AT TDC the cam lobes should be facing AWAY from each other on Cyl #1 (from memory). Oh and by the way, this needs to be done with the cam chain tensioner in place as not having it IN will upset the timing. And this is only the abridged version of how to do it...following Haynes step by step is the proven course.

Easy. Huh!?

 

That, my good friend from OZ ... is exactly why the Yamaha Engineers designed it NOT to be easy and to require absolute precision ... else-wise, someone would be able to ruin a magnificent piece of mechanical engineering without even trying!

 

So i've made several attempts to get in dead on and I seem to get the same result. Namely, that when I give the crankshaft two full rotations the marks on the cams are just slightly behind: there's just a little slack that I can't get rid of when I line up the sprocket with the boss.

For clarification: what are the indentations that I'm supposed to be looking for through the holes? "and the indents can be seen through the holes while the side plate is still lined up with the relevant marks..."

There are indentations near the teeth on both sprockets. On a spare motor I have, I checked and when #1 is TDC those dots are not visible.

I'm happy to spend the time getting it right, but I'm wondering if the chain has stretched a little, and there's no way of getting it bang on. After all, I've tried every configuration and done everything I can to get all the slack out.

 

This is a quote from a XJ550RH service manual and is the same method I used on my XJ750RJ.

"Rotate each cam shaft until the dot on the cam is aligned with the arrow on the center cam cap"

I remember thinking that the "dot" on the cam is pretty tiny for an alignment mark.

I not aware of any hole to look thru, and there are no alignment marks on the cam sprockets.

 

Re indents on the cam.

On my 900, at the end of the intake and exhaust cams there are small indents (like semi drilled holes). These are located on the end round cam bearing which slots into the bearing housing which is integral in the cylinder head.

Once the cams are in place the cam bridge (or caps) are slotted over the bearings and bolted into place. The end cam cap should have a hole on the top through which you should be able to see the indents on the cam bearings. The cam caps on the ends only fit one way from memory and this procedure is a good starting point to knowing where the cams should line be at the point of mounting the sprockets etc.

When the holes on the cam bearings are visible through the holes through the cam caps the TDC mark on the side plate should line up with the relevant indicator. Memory has it though that the '83 model may be somewhat different from '85 or later models as far as where the indicator may be.

It's not a difficult job, just an exacting one trying tio ensure several factors have been covered: cams are in the right position verified by seeing the drilled indents on the cam bearing through the holes in the end cam caps, line up of the TDC mark on the side plate, mounting the sprockets with chain onto the bosses without moving anything(!!?? fun procudure that is...) and then ensuring that after a couple of manual revolutions of the engine everything is pretty much in place.

Anyone with a Haynes manual might like to scan or copy the relevant section and or photos of this explanation. I could possibly do it but it would have to be next week.

 

This is from a XJ550 Yamaha manual...... no holes to look thru.... just line up the dot with the arrow.

 

Karl:

It is that way on 900's. The smaller displacement Bike's have alternative methods for lining up the Cams for initial timing.

The 750 has a drilled dimple that lines-up with a small pointer on the Thrust side of a Cam Bearing Cap.

I like the way it is on the 900 ... because there can be NO mistaking the sight of those drilled-in dimples on the 900's Cam Caps.

The Haynes for 650 and 750 Fours don't have the same information that's shown in the separate Manual covering the Inline Four 900's.

 

Thanks for the help all. It's running. So, I've got a photocopy of the "engine" chapter. Can't remember if the library had a Haynes or Chilton. Anyway, that was my guide (besides you guys).

Just to clarify, I had the cams lined up, #1 at TDC, but there was no physical way to get all of the slack out of the chain between the crank sprocket and the exaust sprocket with the holes lined up. I checked to make sure the chain guide was in it's proper place, but I still couldn't get all of the slack out. So, when I turned the engine over, the cams were both a little behind. (Just a few degrees) And still are. But it seems to be running fine.

When I got the bike, I ended up spliting the case. I noticed that a brass tube to the cam chain oiler was broken. Who knows how long it had been like that for. So, perhaps there's more wear on that chain that is to be expected.

Regarding the indentations on the sprockets themselves, I've got a spare motor, and I noticed that the indentations are not visible at TDC. THere're down below. So, that's how I installed my sprockets.

I'm still a little worried about my failure to get it dead on, so if anyone has futher suggestions, I'm all ears.

cheers

 

The sprockets don't have any alignment marks on them.
You align the cam dot to the arrow on the cam bearing cover, then "jockey" the sprocket bolt holes to the cam mounting points, without rotating the crank shaft and keeping the slack out of the cam chain.
Rotate engine and check the alignment between the dot and the arrow.

 

Right, that's what I did. No movement, no nothing. Still a little slack.

 

For this to get done right ... you are going to need to retime the engine from "The Git-Go"

You provide the Slack by removing and resetting the Cam Chain tensioner.
Then you do the Cams
TDC #-1
Set Cams on marks
Pull Slack up from the Crank to the Exhaust Sprocket
Across the Bridge
Over the Intake Sprocket
Let fall off the Intake Sprocket side
Do the Jockeying to get the sprockets on
Release the tensioner removing all slack
By-hand rotations to check for precision ...

If you have it ... you torque and button-up.

If you don't ...

Back to "GO" and Do Not Collect 2-Hundred Dollars.

And ... therein is the reason that they didn't spline the sprocket.

You are NOT supposes to settle for anything but DEAD NUTS -- RIGHT ON THE DOUGH!

Eventually, what ever slight error you think is OK ... is going to be like stepping over a dead log and having your shoe come right down onto a coiled-up Diamondback Rattler.

At High revs you'll lose power
You might burn a valve
Something not good you wouldn't wish for.