Topic: Manual Cam Chain Tensioner from Ape

[luckylefty]

saw some post on these but anyone have experience on these ? I am on a 74 SOHC my mech recommends to replace to these.

[BenelliSEI]

Why would he recommend that??? Those devices are perfect for generating way too much chain tension and stretching the crap out the cam chain.

If he suggests it will eliminate chain “rattle” ask him to set the cam chain tensioner as described in your manual, adjust the valves, set the timing and synchronize the carbs with a manometer instead.

I’ll be very interested to hear what others have to say. I don’t see the purpose.

[MauiK3]

The cam chain needs a prescribed amount of tension that the factory spring applies. The manual adjuster allows the user to get the tension way out of spec. They may be ok for drag bikes and such where you expect to be taking the engine apart but for longevity on a street engine I'd stay away from it.

[newday777]

I agree, stick with the Honda parts. New slide and tensioner wheels are still available from Honda.

[cooldrum]

I just did a thorough tune up on my K4.  Only 34K miles.  Stock ignition, replaced plugs, points, condensers and tested the plug caps. Set the timing, valves adjusted and synced the carbs.  Adjusted the idle and clutch rattle gone.  Pulls like a freight locomotive now.  Oh, did the chain tensioner too.  Just takes patience to dial it in.  Cheers!

[madmtnmotors]

Manual tensioner runs the risk of overtensioning the cam chain with potentially catastophic results. Stock tensioner carries no such risk. A good carb sync will quiet things down more than anything. Mine will idle smoothly all the way down to 800 rpm with a good carb sync.

You might consider finding a new mechanic...

[craz1]

I agree, you run the risk of over tightening that chain. I ran one on the Z1 for a bit but converted back to the stock unit. You won't have any issues with the stock adjuster as long as you are not consistently bring it up to redline and missing shifts.

[luckylefty]

thank you all!

[rotortiller]

If you set the manual tension force correctly it's no different than the OEM. The OEM spring tensioner locks the tension in once set, just like the manual type. Both will work fine but only if set correctly. I see no advantage of the manual springless type for the SOHC bikes, however they are a good replacement for some of the newer ratchet self tension mechanism modern bikes often employ.

[Phoenix]

I had read somewhere that you can adjust it by ear.  I tried it by tuning the noise out.  Had it that way for years with no problems.  Maybe I was just lucky.  Just replaced the cam chain and adjuster and adjusted it per the book.  Noisey.

[bert96]

Is the oem tensioner spring available?

Bert

[PeWe]

The manual tensioner was designed to cope with gear downs with high revs better than stock?
Less risk chain jump a toth or two.

[HondaMan]

The manual tensioner was designed to cope with gear downs with high revs better than stock?
Less risk chain jump a toth or two.

That's why it was created, PeWe: in roaderace engines with 11,000+ RPM racing cams the roller of the tensioner is made of harder materials (like steel or hard aluminums) and the manual tensioner is used to set the tensioner a little tighter in a specially-controlled way. Those chains have real short life, too.

That said: the regular tensioner can increase tension, too, by pressing in on the back of the shaft while the bolt is loose. Honda's early manuals expressly said, "Don't to this". Honda removed teh proper procedure, though, when they made their green Factory Maniuals. It was shown in the loose-leaf 3-ring binder pages they started with.

The only aftermarket manual I've seen that has the CORRECT method is in the Chilton's manual (pgs. 47-48) where it shows the engine turned forward to 15 degrees past TDC of cylinder #4 (i.e., just past the corner of the spark advancer's baseplate, when the #4 intake valve starts to take out its slack), then it says to release the tensioner's bolt at that point: I might add, though, to give the shaft inside a little push, using one of the long screws you just removed from the timing cover, in case the shaft got stuck. They do stick once in a while! Then just retighten the little bolt-nut.

[newday777]

The manual tensioner was designed to cope with gear downs with high revs better than stock?
Less risk chain jump a toth or two.

That's why it was created, PeWe: in roaderace engines with 11,000+ RPM racing cams the roller of the tensioner is made of harder materials (like steel or hard aluminums) and the manual tensioner is used to set the tensioner a little tighter in a specially-controlled way. Those chains have real short life, too.

That said: the regular tensioner can increase tension, too, by pressing in on the back of the shaft while the bolt is loose. Honda's early manuals expressly said, "Don't to this". Honda removed teh proper procedure, though, when they made their green Factory Maniuals. It was shown in the loose-leaf 3-ring binder pages they started with.

The only aftermarket manual I've seen that has the CORRECT method is in the Chilton's manual (pgs. 47-48) where it shows the engine turned forward to 15 degrees past TDC of cylinder #4 (i.e., just past the corner of the spark advancer's baseplate, when the #4 intake valve starts to take out its slack), then it says to release the tensioner's bolt at that point: I might add, though, to give the shaft inside a little push, using one of the long screws you just removed from the timing cover, in case the shaft got stuck. They do stick once in a while! Then just retighten the little bolt-nut.

Re-tighten at the 'little push' point or the static spring tension once you verify the tensioner moves freely?
Seems like I remember learning back in the mid 70s at the shop by the guys out back to push a little, used an allen wrench.

[HondaMan]

The manual tensioner was designed to cope with gear downs with high revs better than stock?
Less risk chain jump a toth or two.

That's why it was created, PeWe: in roaderace engines with 11,000+ RPM racing cams the roller of the tensioner is made of harder materials (like steel or hard aluminums) and the manual tensioner is used to set the tensioner a little tighter in a specially-controlled way. Those chains have real short life, too.

That said: the regular tensioner can increase tension, too, by pressing in on the back of the shaft while the bolt is loose. Honda's early manuals expressly said, "Don't to this". Honda removed teh proper procedure, though, when they made their green Factory Maniuals. It was shown in the loose-leaf 3-ring binder pages they started with.

The only aftermarket manual I've seen that has the CORRECT method is in the Chilton's manual (pgs. 47-48) where it shows the engine turned forward to 15 degrees past TDC of cylinder #4 (i.e., just past the corner of the spark advancer's baseplate, when the #4 intake valve starts to take out its slack), then it says to release the tensioner's bolt at that point: I might add, though, to give the shaft inside a little push, using one of the long screws you just removed from the timing cover, in case the shaft got stuck. They do stick once in a while! Then just retighten the little bolt-nut.

Re-tighten at the 'little push' point or the static spring tension once you verify the tensioner moves freely?
Seems like I remember learning back in the mid 70s at the shop by the guys out back to push a little, used an allen wrench.

I've done it both ways: tighten with the push happening, and after releasing it. On the one bike where I got back inside a few months later after I/we were using that push& hold method to set the chain, the rollers were much more deeply marked while the front slipper guide looked virgin. On the others that I/we set normally, there was noticeably less wear on the rollers, but more on the front slipper guide. The "push and tighten" one seemed to need it done more than the other ones that season, too. So, after that I quit applying the extra tension myself. Those 3 bikes were flogged pretty hard at the tracks, always in the upper 1/3 of the RPM range when running most of the short races (50 milers, mostly) that we had then.

In retrospect, I think it is easier on the chain if it has less tension, which matches up well with the drivechain scenario: the less tension it has, the better the oil can wick itself in between the pin and roller as the chain exits either sprocket (top or bottom) before it hits the other sprocket. I think (but can't prove) that this happens as it snakes over the tensioner rollers, too. The more force that is applied to the roller as it enters the sprocket, the more oil is wicked out just then, and the more oil is wicked back in as it leaves, provided the oil doesn't fling out of the sideplates. This is why there is a 'sweet spot' range of diameters for each chain size, above which (too large) the centrifugal force flings the oil off the sideplate, making it unavailable to suck back in when the roller leaves the sprocket, and below which the mass of the oil itself is high enough to fling itself off the sideplate as the link changes direction too suddenly. In between those extremes the ideal environment lives, and in the case of the 750/500/550 engine this relationship is nearly ideal on both ends, until 11,500 RPM.

This is also why the 350F/400F are so hard on their cam chains: the crank sprockets are a bit too small for the high RPM those bikes can do. The tensioners help a lot there by having long 'runs' where some oil can be caught on their chain guides and reapplied to the links: this works well until the bikes are raced, and then the chains just take a beating.

[PeWe]

I know what happen if using the starter when the tensioner is not locked at all. A quick chain jump.

I was lucky it jumped in a way not harming valves nor pistons.
I had to check inside.
Plus verify that the crank teeth were still there, all of them....

Cylinder milled 1mm + head back then was milled 0.5mm might have helped the chain jump
Pistons pockets saved they day/month/year!

A manual tensioner might be tightened better than stock when the entire packagage is 1.5mm lower.
(1.75mm lower when using thin RCS base gasket. Head gasket as the early stock 0.75mm)

Use a stronger stock tensioner spring might help?

[HondaMan]

I know what happen if using the starter when the tensioner is not locked at all. A quick chain jump.

I was lucky it jumped in a way not harming valves nor pistons.
I had to check inside.
Plus verify that the crank teeth were still there, all of them....

Cylinder milled 1mm + head back then was milled 0.5mm might have helped the chain jump
Pistons pockets saved they day/month/year!

A manual tensioner might be tightened better than stock when the entire packagage is 1.5mm lower.
(1.75mm lower when using thin RCS base gasket. Head gasket as the early stock 0.75mm)

Use a stronger stock tensioner spring might help?

Yep, I think you're right on all counts.
I first discovered the too-much-tension issue when working with the [in]famous "Hi-MPG" versions of the 750K4/5 engines where the cylinders are slightly taller than normal (to lower compression a bit). In those engines the cam sprocket is tough to get up onto the camshaft during reassembly because there is almost no slack in the chain, nowadays ESPECIALLY if you have the new thicker head gasket and didn't mill back the cylinders to compensate: if you have also a brand-new cam chain you may find (like I did) that you must first clean all the storage grease out of the chain (in solvent) to get enough chain length to reassemble - or, just mill the cylinders 1.0mm instead of 0.010", and re-bore the O-ring recesses, but that gets expensive pretty quickly.
But...that does make for better compression and more HP in the end, though!

[PeWe]

The standard cylinder and head heights one detail.
I have measured several cylinders to be 85mm.

So milled 1mm make 84 mm cyl height.
Head was milled 0.5mm to shrink the opened chambers by an old home made port job.

Height after 0.50mm off 71.25mm
I think it was stock height before.

The pistons height forced me to ask the shop to mill cylinder so the outer flat edge of the big bore pistons were flush with head upper gasket surface without base gasket.

0.001" (0.25mm) RCS base gasket + 0.003" (0.76mm) MLS headgasket make a squish close to 1mm which is written to be good by the experienced race guys. That worked well.

So pistons that match the cylinder height without milling the cylinder keep up the chain tension.

[HondaMan]

Another 'secret' that was used in those midget-car engines I saw in the 1970s was that they would mill off the cylinders to pop the pistons up closer to the head, then carefully recontour the head chambers to match their hi-domed pistons, clearancing the pistons for the valves. In those 2 engines they had shims under the cam bearings, which I noticed, but didn't realize until much later: they had lost so much cam-chain distance between the crank and cam that they had to raise the bearings to set the cam up higher because the tensioner could not take up the slack: it was out-of-reach distance. I overhead them discussing the issues this caused, which included having to change the valve angles or else the rocker arms in order to stay on the tips of the valves. This was on an engine that pair of guys were building for the 1974 season, and I wasn't there after 1973 to see how it turned out. I remember thinking at the time that it might be easier to use a shorter cam chain, and I knew that using a master link was not an option just because of its low strength - so, I didn't have nay useful advice for them at the time.

[PeWe]

My JE 67mm (890cc)pistons from Dynoman have a better height. No need to mill the cylinder.

They had CR 12.5:1, sparkplugs needed an extra washer to stay free.
Too high compression despite spacious chambers, DP315 cam with less lash causing a huge overlap.

Those pistons crowns now milled 2mm, hopefully OK after that.
JE flat tops are possible to adjust a few mm. Thick material, 6-7mm.

The JE 71.25mm (1005cc) pistons from Dynoman match an  84.5 mm high cylinder.

My older JE 70 mm pistons  (970cc) are lower, 0.50 mm lower than the 71.25mm. Therefore mill the cylinder 1mm, mill the wider groove for sleeves and 2 o-rings too.

Easier if CB750 pistons have an height for stock cylinder which I have seen to be 85.0mm.
(My old Mitutoyo vernier calipers from the 80's might differ a little)

This to ensure cam chain tension, even when used with eventual stretch if a ca: 2mm lower cyl-head package will cause chain slack issue to be handled by tensioner. Maybe not that much.

When at it:
http://www.cyclexchange.net/Tech%20Tips%20Cylinder%20Head.htm
- From CycleX -
Cylinder head thickness: 2.842" (72.1868mm)

Cylinder thickness: 3.334" (84.6836mm)
At full operating temperature the cylinder & head can grow .015 or more.