75 KZ400D Balancer Issues

S

sosedoff

New Member
Hi all,

Backstory: I've been slowly rebuilding my 75 KZ400D engine. Main reason why i got into
the bottom end is to replace the broken cam chain tensioner. I haven't figured out how to
remove the tensioner without removing the whole balancer at the time, so i got all the parts
out of my way and replaced the part in question. All good there.

The trouble started when i began to put the balancer mechanism back. I have 2 manuals on
hand - Clymer and the KZ400D/S print copy. Each counter balancer body has 4 mounting
bolts. Clymer lists 8.9-9 (something) ft/lb torque spec per bolt, while the original manual
has 16-18.5 ft/lb. The balancer bearing cap bolts (big 4) have the same specs in both manuals.

I decided to go with original manual's spec. Most counter weight bolts that i torqued were around
14 lb/ft. Im suspecting that something is up with the spec because i felt like i was close to stripping
the thread. One of the bolts, however, didn't torque even over 8 ft/lb. The tread is messed up. Now
that i tried to tap it (just to clear the tread) i cant torque it even over 4 ft/lb.

First, what's the proper torque spec for the counter weight bolts ? Second, what are my options for
fixing the last bolt?

Thanks!
 

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To repair the thread you will need to install a helicoil.
The kits usually come with, drill, tap & coil.
 
Does that mean i will have to get a new bolt of a different size? My backup plan was to use the
red locktite and lock the bolt as much as i can since i dont really want to reopen this engine again.

On the other hand i just want to make sure i've done the job properly so nothing gets loose.
This is my first project so i feel really intimidated by anything that comes up.
 
Does that mean i will have to get a new bolt of a different size?
Click to expand...
No - you use the original bolt. You drill out the original hole with the drill provided in the kit. Then you cut an new thread using the tap provided in the kit. Then you screw in a stainless steel coil which creates the new thread for the original bolt to screw into.

My backup plan was to use the
red locktite and lock the bolt as much as i can since i dont really want to reopen this engine again.
Click to expand...
You would be better off throwing the engine in the rubbish bin. The bolts on the balancer are critical and by only having one bolt holding the bearing the single bolt remaining will soon fail and do god knows what to your engine!!!!
A helicoil into aluminium casings should be stronger than the original thread due to the larger surface engagement of the helicoil.
Half and hour spent now will save a lot of tears later on!
 
This is my first project so i feel really intimidated by anything that comes up.
Click to expand...

Don't be intimidated by this issue, once you have worked out the bolt thread it is easy to get a kit off Ebay or elsewhere. It is most likely M8 (measure about 7.8mm) or M10 (measure about 9.8mm) then you just have to confirm if it is a standard thread pitch or a fine thread pitch. Easiest way to confirm the pitch is buy a standard pitch bolt (most readily available) and see if the threads line up with the Kawasaki bolt threads. If the Kawasaki bolt threads are closer together then you need the fine thread kit. For your information M8 standard pitch is 1.25mm and fine pitch is 1.00mm, M10 standard pitch is 1.5mm and fine is 1.25mm. Pitch is the distance from ridge to ridge.

If you are careful and take things easy you do not need a drill press or mill to drill the hole out. Just use and electric drill and the drill bit will follow the original hole as long as you do not force things. The most important thing is to make sure you do not go any deeper than the original hole. You will feel it hit the bottom, then immediately remove the drill.
To cut the thread, a tap wrench will help to get it to cut evenly. When you first start you need put downward pressure to make sure the tap is cutting. Once you have cut a full revolution the tap will pull itself down. To cut the thread you turn it in 1/2 a revolution and then out 1/3 of a revolution, this breaks the swarf and stops the tap jamming, also use lubricant like WD40. Keep the process going until you tap the thread all the way down.

Once the thread is cut get all the swarf out and use the tool provided in the kit to screw in the coil.

You will be surprised that it is not that hard to do, and you will be bloody proud of yourself once it is done.
 
To be 100 per cent sure about the thread pitch and size go to your local hardware store and check with a nut. A fine thread nut will not screw onto a normal thread one....
This is the safe way.
Don´t glue anything in that area!
 
1] Use a Time Cert not a heil coil.
2] Learn to convert metric to inch measurements and visa versa.
3] Clean and lubricate the threads if the fastener is to be torqued down.


.
 
Use a Time Cert not a heil coil.
Click to expand...
Learn something every day - the time cert does look like a good option. You do not have to get rid of the drive tang!!! And it locks itself in.
 
If you have never done either a Helicoil or a Time Sert I would suggest taking the engine to a machine shop that has.


Apart from the fact that they will do it properly, you will have to buy an entire insertion kit for either of those two solutions that you will probably never use again.


In the end it will probably cost the same, but to do it yourself it's not really something you get a second chance at getting right.
 
Well, its been a while since i've done anything on the engine. Work got in the way, but i have to get back to it.

So, i got the info on the bolt (M6 x 1.0). I will call the machine shop and see if they can do the fix the right way,
in the mean time - if i go with helicoil what insert length should i look for? The bolt has a pretty long thread, but i'm
not sure the insert has to match that.

Thanks again for all the replies, this balancer issue has been a real show stopper for me.
 
For anyone who might find this thread useful, i got back to the rebuild and did drill/tap/insert a helicoil today.

Since the thread was pretty long i had to locate the longer inserts, 3D-size worked well (3-x of the bolt diameter).
These are shipped from Japan, unfortunately. Before doing the job on the case i first tested the procedure on a block
of wood just to make sure i wasn't doing anything wrong.

To drill the thread i had to remove the metal dowel that sits underneath the balancer bearing. This was a bit
tricky, but after soaking it with BP Blaster i was able to wiggle it out with pliers, that did leave some small
bite marks which i later smoothened out with a wire wheel.

I haven't finished the final assembly yet, but i noticed something: when i put the bolt back in about half way it
does not feel snug, i can feel a slight movement (left/right), same happened with the wooden block i was testing
first. When the bolt is fully in it feels alright.

Did i mess something up?
 

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