The Curse of Odot

Yamaha FJR Motorcycle Forum

Help Support Yamaha FJR Motorcycle Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
It would be good to know what MamaYama did when they up-dated/superceded the cam-chain-tensioner part #. :huh: :unsure:
I'll let ya know when mine comes. McCoy is sending it my way, I'll see if anything is different. Gary is keeping 2 in stock due to info coming from here-I told him this latest episode may give him a few more orders. Cost is $66 by the way.
You gonna pull a Brodie? Take apart a brand new, perfectly good part?

Post plenty o'pics.

 
Me again. Thinking again.

Nobody said anything about my chain guide, in post #90, and I know I'm not helping RH, but I'm thinking about something that could prevent a repeat in other bikes, if it were feasible to build. Just a thought exercise, really, since the tensioner's not a multi-thousand dollar part, but just wondering what else might be done to prevent such a catastrophe. Apparently dimpled pistons is not the answer.

I also got to wondering if a switch could be built into the tensioner somewhere so that a lack of pressure equals a kill switch?

Granted, if you're out riding, the engine's gonna be turned over by the tranny until you clutch, but if I recall correctly, both of these happened on startup. If the tensioner or something in the chain guide was smart enough to shut off the motor when Bad Things happened, maybe not so many Bad Things would happen.

 
Me again. Thinking again.Nobody said anything about my chain guide, in post #90, ....if it were feasible to build. Just a thought exercise, really, since the tensioner's not a multi-thousand dollar part, but just wondering what else might be done to prevent such a catastrophe.
It has merit. There are (and have been around for decades) similar devices for countershaft sprockets for final drive chains. They're not so much to keep the chain from slipping on the sprocket (altho, with a close fit, they'll do that) -- but, they're there to keep a broken chain from damaging the case.

A close fitting block of the same material as the exisiting guides (high molecular weight poly...?) may achieve what you seek -- keeping a loose chain attatched to the sprocket. Yet, ultimately, all 3 sprockets may need such a device...?

Apparently dimpled pistons is not the answer.
They could be -- along with reduced cam lift and duration. IOW: a 'non-interference' design. One problem with a DOHC design is not only can errant valves hit piston tops, they can strike other (opposing) valves. Reducing engine output by giving all those pieces sharing the combustion chamber their own 'space' would probably not be desireable for most...? :unsure:

I also got to wondering if a switch could be built into the tensioner somewhere so that a lack of pressure equals a kill switch?
That sounds quite difficult, to me (but there are waay smarter folks, than me, frequenting this Forum).

Granted, if you're out riding, the engine's gonna be turned over by the tranny until you clutch, but if I recall correctly, both of these happened on startup. If the tensioner or something in the chain guide was smart enough to shut off the motor when Bad Things happened, maybe not so many Bad Things would happen.
"Fail-Safe" -- certainly a good idea (especially considering the alternative). :(

 
The fail safe, barring an actual spring breakage, is to pop the cap off the tensioner, and give it a left twist. The spring can be too weak to advance the mechanism, yet still, IMHO, be strong enough to prevent the adjuster backing itself off. The left twist would adjust the tensioner, just like a manual tensioner would operate-think of it as a semi-auto. At the same time, note how much you are able to turn the screw-should turn slightly if at all. Anything more than 1/8 of a turn spells trouble-the spring has weakened, in which case a manual adjustment can keep you going till new parts arrive, or broken (can be determined by turning clockwise, winding the spring). If the spring won't wind, you aren't riding anywhere, and you can congratulate yourself on having staved off valve destruction, unlike our forum unfortunates.

Theoretically, if the spring remains intact, one could manually advance the tensioner at oil change time indefinitely, or until the chain had so stretched that it's impossible to take up the slack anymore. Take comfort in the fact that cam chains rarely break-at least in my experience, though anyone could be the first to announce it here. I wouldn't hold my breath. I just know I plan to check and adjust the tensioner at each and every oil change from here to eternity-not complicated, and insures against stratospheric engine damage, as well as helps monitor chain health.

 
Last edited by a moderator:
I also got to wondering if a switch could be built into the tensioner somewhere so that a lack of pressure equals a kill switch?
It is much easier to put a automotive knock sensor on the exhaust cam shaft, when the pistons hits the valves it will trigger the knock sensor. Then the Meter Assembly can then display: YOU ARE PHUCKED thereby creating a fast, easy troubleshooting process.

An improperly tensioned cam chain will have characteristic wind-up and snatch [/dirty minds] motion, you can see this in the chains on some poorly adjusted chain drive bikes. This motion can easily be sensed and monitored by the ECU. It is simple for the diAG screen to pop a warning code or the ECU to issue an alert and inhibit starting until the issue is fixed. A sensor like the TPS is more than up to the job to detect motion of the slipper that is improperly tensioned by the CCT, and the software code would be simple. It would cost a data channel to the ECU but the software monitoring overhead would be low.

Or, Yamaha could use a better quality high velocity cam chain that won't require as much compensation. Or change the chain slipper to have a bigger back side bump so that the CCT will engage the slipper with only 3/16" to 1/4" of the plunger extended so that the CCT can make better use of the internal spring tension. I would add another OR but Yamaha apparently has redesigned the CCT because it has a new P/N.

Edit: I see there has been a lot of activity while I was typing this, now to go back and read what was written.

 
Last edited by a moderator:
Or change the chain slipper to have a bigger back side bump so that the CCT will engage the slipper with only 3/16" to 1/4" of the plunger extended so that the CCT can make better use of the internal spring tension.
Or a selection of thicker end-caps for the plunger. Kinda like a shim selection for the valves living over in the garbage can. (or compression welded to the head)

Edit: Actually, a thicker end-cap is feasible. The end-cap on the plunger is held in with a split compression pin. Easily removed, new, thicker cap installed, pin replaced. Voila!

cct9.jpg


 
Last edited by a moderator:
This whole thread just goes to show how mechanically unreliable the fjr is.

 
DAMN! Howie,

I've been busy since we did the tank swap and have just checked in to see if your new fuel pump had done the trick and I run into this tale of woe. What a pisser

If there is anything I can do to help, short of giving you major parts of my motor let me know. If you find an engine or head and need a transport to pick it up give me a shout.

 
Last edited by a moderator:
DAMN! Howie,I've been busy since we did the tank swap and have just checked in to see if your new fuel pump had done the trick and I run into this tale of woe. What a pisser

If there is anything I can do to help, [SIZE=14pt]short of giving you major parts of my motor[/SIZE] let me know. If you find an engine or head and need a transport to pick it up give me a shout.

Some friend YOU are! :) :) :)

Thanks...unless you actually wanna let me borrow your cylinder head, I think I'm pretty much on my own. I'm investigating a couple of angles. Some good...some NOT so good. Whatever I decide, it's probably gonna cost me one of my bikes. :angry:

C'est la vie.

The REALLY sad thing is your loaning me the tank/fuel pump gave me a 100% diagnosis of my problem, which was corrected with a replacement.

I was literally hours (and a cam chain) away from riding. Sigh!

 
Last edited by a moderator:
I've got a cylinder head that I can give you. I think there are only 6 valves that are still stuck in it. There is a bit of damage around several of the valve guide areas but a little JB Weld should take care of it. I've also got a cam chain, a CCT, all the springs, buckets and probably all the valve keepers.

 
I've got a cylinder head that I can give you. I think there are only 6 valves that are still stuck in it. There is a bit of damage around several of the valve guide areas but a [SIZE=14pt]little JB Weld should take care of it[/SIZE]. I've also got a cam chain, a CCT, all the springs, buckets and probably all the valve keepers.
:rofl:

That would be the "High Pressure/High Temperature" JB Weld, right???

 
Got a question for any of you doinks who've had your Feej's cylinder head off....

There are two 6mm socket screws that attach the head to the block, separate from the main head bolts under the valve cover, at the extreme right-hand side of the head (left side in this pic):

03FjrHeadCombustion.jpg


Those bastards are buried about 4 inches from the top of the head RIGHT against the frame:

servo_and_vacuum_lines_redone.jpg


How in James Earl Jones to you get those fucks out???

IF I can get to them, I'm yanking the head off this weekend to survey damage and start making plans to either resuscitate or euthanize the Silver Streak.

 
Last edited by a moderator:
Got a question for any of you doinks who've had your Feej's cylinder head off....


03FjrHeadCombustion.jpg


What the Hell else would it be? "red arrow" a manatee testicle???

Those bastards are buried about 4 inches from the top of the head RIGHT against the frame:

servo_and_vacuum_lines_redone.jpg


How in James Earl Jones to you get those fucks out???

Sawzall ya dolt!
Can't lower the motor none? Damn, I'd like to know how the hell they get em out..

:jester:

 
[snip'd jackassisms]
Can't lower the motor none? Damn, I'd like to know how the hell they get em out..

:jester:
That has me wonderin', too. Maybe just pull the front engine mount bolts and pivot the motor down and forward???

Maybe have to pull the driveshaft at the u-joint to prevent over stressing the joint.

 
Top