The spacer is now inside the mechanism. Below you will see that I unwound the mechanism almost all the way out.


This next pic is the inside of the housing that the mechanism goes into. You can see the cross section of the spring in the middle. Make sure you line up the groove that the screwdriver on the mechanism would go into with that part of the spring when assembling the two pieces.

Edited by Charlie755, 08 May 2012 - 02:58 PM.

This next pic is the two pieces put together with the spring cross section in the flat head groove of the mechanism.


Next while holding the assembly together take a small flat head screw driver and turn the screw in until it locks the mechanism in the retracted position.


Last thing to do is install the small snap ring/circlip pictured here at the end of the housing.

Thats it! The timing chain doesnt end up as kinked up as quickly either though I still replace the timing chain every 40hrs when I do a piston just for cheap insurance and to not wear out the crank gear prematurly with a bad chain.

Edited by Charlie755, 08 May 2012 - 03:04 PM.

Thats a pretty interesting little mod there. I've never seen it done before. Does that help the chain stay tighter?

Charlie755, on 08 May 2012 - 03:02 PM, said:

Hey Charlie, this is the kind of stuff that keeps riders informed as well as being an awesome contribution. Thanks for taking the time to show a very critical step that can be done if members value their valve train.

I just reconstructed what you did with a left over case dowel or cylinder to case dowel I should say, because I think those are the thinner gauge ones that I cut down to 7.5mm for the length because 8.5 and 9.5 mm were a tad long for it to be able to click lock into position every single time; but it does without a doubt, work.

The length of the dowel can be temperamental, and I understand your 8.5~9.5mm leeway for the length, because if it doesn't click lock, one can just take the homemade spacer to the grinding wheel and knock off slight increments until it will allow a positive engagement of the locking mechanism.

The OEM part number of the dowel that I cut down is: PIN, DOWEL #99530-10116-00 and it slid like a glove just over the worm gear, but yet right inside the shell they already have over the worm gear. Your measurements are spot on and if my old tensioner wasn't worn out, it most definitely would work with the 8.5/ 9.5mm dimensions you gave for the length - I'm certain of it.

What I'm not certain of, is if OEM PIN, DOWEL #93612-16254-00 has the same dimensions as the PIN , DOWEL #99530-10116-00 because the case dowels are a thicker gauge, but may still work - I couldn't find any left over case half dowels.

EDIT: I just found a case half dowel, and it slid over the worm gear also. Looks like either of the dowels will work, just have to cut them to the right length.

I didn't think that it would be able to click lock into place for removal, but it did, and I commend you for sharing this valuable insider tip that every TT member should know.

Edited by nokickstandsallowed, 08 May 2012 - 08:35 PM.

MXskater.

It doesn't allow the timing chain to skip teeth in the event that the tensioner kicks back. This happens rarley but when it does with a stock auto tensioner its can be catastrophic.

Edited by Charlie755, 08 May 2012 - 08:39 PM.

nokickstandsallowed, on 08 May 2012 - 08:26 PM, said:

Thanks for your input on this too man. Much appreciated.

By the way the part I originally used was a steel spacer used on the plastics of a 2003 YZ85.

Charlie755, on 08 May 2012 - 08:44 PM, said:

Your Welcome.
I was thinking either a steel spacer or dowel - the dowels are pretty tough between the case halves and should cut it; but yes, I would go with a steel spacer.
The dowels I pulled from the case halves are magnetic, and the ones from the head to cylinder are non-magnetic I think. I would feel confident in using the ones from the case halves, as they are a thicker and better gauge of material than the cylinder to cylinder head ones.
Heck, maybe even the ones from the top of the case to the cylinder - I think those are magnetic as well, and the same gauge thickness as the case half ones.

Edited by nokickstandsallowed, 08 May 2012 - 08:55 PM.

nokickstandsallowed, on 08 May 2012 - 08:51 PM, said:

I agree on the dowels from the case halves for sure. I like the thickness of the dowels as they are close to the 2 mil thickness. I wouldnt trust the thinner cylinder or cylinder head dowels as they are so thin.

Heres a couple more pics of my progress. In the second pic you can see the modified clutch actuater arm (painted black) that I installed.





The project is going to be slow going for a bit. I just dropped my suspension off last week and was informed yesterday that I am looking at about $900.00 to have it done up. Ouch!!! I already knew it would need heavier duty springs and a revalve but unfortunatly the fork tube on one side had worked its way loose of the axle mount so they need to be replaced. I know the axle mount is called something else ha ha but I am no suspension expert. He is also modifying the spring setup on the forks by adding a small spring at the top of the main spring so the suspension is plusher while going through its travel but if it bottoms out will take the hit instead of my arms. Next big purchase is going to be the Lukes Racing big bore and a Wiesco clutch basket kit.

Edited by Charlie755, 09 May 2012 - 07:27 AM.

I figured since I still have the old piston from this bike I would show pics of the aftermath. Yes that is a valve stuck in the piston. Amazingly none of the material from the piston broke off and dropped into the crank case. As posted already I replaced the crank anyway. This wont be an issue again since I did the tensioner mod.

Charlie755, on 10 May 2012 - 01:45 PM, said:

No it won't, but I was wondering about something else that may cause it that lurks in the back of my mind.
Since I have been running a MCCT, I have virtually had no valve train issues; but, I have mercifully almost forgotten about my valve springs. My valves haven't moved forever (like 70+ hours so far) and I was wondering, how far should I push the OEM springs on them? Should I wait until changing the valves or should I get their seat pressure and spring free length measurements. If I keep waiting on my valves to move, it looks like it could be another 50+ hours before they do, and I can't just ignore the springs because the valves aren't moving.

I just don't want a fatigued spring to cause valve float/bounce and end up looking like your picture above.
Whats the longest you've gotten out of OEM springs with no issues?

nokickstandsallowed, on 10 May 2012 - 02:50 PM, said:

Excellent question. I have never ran stock valve springs past 80 hours. This is just my personal preferance so you dont have to take it to the bank per say. I typically just replaced my valve springs every 40 hours when I did the cam chain and top end. That was on my sons bikes when he raced mind you. You can totally go off of spring free length and follow the manuals recommendations but I prefer the peace of mind. When you total up the cost of 5 new valve springs (about $33.00) its pretty cheap. I would also replace the valve seals at that time which was about $20.00 for all 5.

Realistically for my riding level and what I am doing with this bike I will do this about every 80 hours or every other top end. My son raced at the intermediate/B and pro level and was hard on engines so I really tried to stay ahead of any likely failures with his bikes. Also you already have the head off when your doing the top end so it doesnt take much more effort to change out the springs as long as you are comfortable doing so.

Thats just my 2 cents on the subject.

Edited by Charlie755, 10 May 2012 - 04:56 PM.

Charlie755, on 10 May 2012 - 04:54 PM, said:

Excellent answer. You actually helped me make a decision I didn't want to make before pulling the head.
Here is the thing that is bothering me though:
I already know how much longer I can get out of a cam chain because of my mod (I still change it out at 40 or 50 hours though), and I'm thinking because I have been riding the bike like a grandma and the valves haven't really moved to speak of, I think I'm not gonna push them (springs) past 80 hours (seems very logical) on any given set of them, even though I've been riding like an 80 year old - that isn't by choice either or maybe I mean it is (ahh what am I saying) - you know how it is, the bank account determines how far around that throttle gets twisted each month sometimes -   .

Edited by nokickstandsallowed, 10 May 2012 - 05:18 PM.

Charlie755, on 08 May 2012 - 08:36 PM, said:

I'm a little bit confused when you say "kick back." I thought the ACCT had a ratchet mechanism that prvents it from retracting unless you unscrew it. So does "kick back" mean it goes forward when the chain is loose for a second? And if so, how does this mod prevent that? If anything, it would make it worse, right? Btw, did you have any major trouble with doing this mod? I think I'm gonna try it but if it's a pain in the ass I might skip it.

Edited by AKmotorider, 09 October 2012 - 06:40 PM.

AKmotorider, on 09 October 2012 - 06:40 PM, said:

The "kick back I am reffering to is the tensioner retracting on decel. When this happens it lets the chain go slack and allows it to skip teeth and cause the valves to hit the piston in most cases. It is very rare but it does happen. On the Yamaha it is not a ratchet as you can see in the pictures its a threaded shaft with spring tension. Its not supposed to retract but it does not positivly lock in like a Kawasaki or Suzuki tensioner does.

I add a spacer so that the tensioner cannot retract far enough (in the event of a kickback) to allow the chain to skip teeth on the crank or camshaft gears.

my buddies 09 has a 290 athena kit and it is hard on the camchain and rear gude.keep an eye on it.he does the piston changes at no more than 50hrs,they look pretty good,but the chain is always kinked and worn out.i have a 269 kitted 09 that runs just as good,the headwork on mine is alot better and the head gasket has only leaked one time,this was a stock cylinder that was bored and replated by millenium.the piston was a 13.75 cp unit.cams are gytr and a fmf megabomb and 4.1 muffler.either way you go,you should be happy.

Charlie755, on 10 May 2012 - 01:45 PM, said:

The aftermath of what? I can see your engine obviously blew up, but how did that happen? Do you blame the ACCT? Is that why you did the mod to it in the first place?

AKmotorider, on 12 October 2012 - 11:09 PM, said:

Yes that is exactly why I did the mod. Maybe I am not explaining it very well. The cam chain tensioner when engauged keeps tension on the timing chain. In rare cases the tensioner can kick away from the chain guide when chopping (letting off completely) the throttle. This lets the timing chain go slack and can cause it to skip teeth and throw the timing off resulting in one or more valves hitting the piston. Make sense? The spacer I put in the tensioner prevents the tensioner from being able to kick back far enough to let the chain tension to be loose enough to allow it to skip teeth thus preventing castastrophic failure.

Look at the first pic I took of the mod. You can see in the first auto tensioner how much shorter it is than the second one. The second one is with the spacer I put in it. That is what prevents the chain from getting enough slack to skip teeth.

Edited by Charlie755, 13 October 2012 - 02:32 PM.

Charlie755, on 13 October 2012 - 02:30 PM, said:

I understand perfectly what the tensioner does, how it can cause an engine failure, and the mod you did to it. What I was mainly trying to ask is did this happen to you?

AKmotorider, on 13 October 2012 - 08:45 PM, said:

Yes that is from one of my sons race bikes before I started doing this mod. Aside from an 06 that dropped a valve because of a factory valve issue this was our only other engine failure