1973 ignition 450wr

Hey guys,

Tonight I started to dig into my 73 450wr a bit to make sure it will run for the ISDT reunion in August. I put in some fuel and started giving it some kicks. The bike has pretty good compression. Kick-kick-kick, never heard a pop. I pulled the plug, let it hang on the side and kick to check for spark. It would spark once for every three kicks or so. I put one of those adjustable spark testers on and if it was adjusted to where the gap was almost closed and it would spark with every revolution. I tried to clean the points through the slot in the flywheel, blew it out with compressed air and tried again. There really wasn't any improvement. Very weak spark. I then shortened the gap in the spark plug and installed it in the bike. I kicked it a few times but heard nothing. I thought about spraying a shot of starting fluid in the carb. But, I didn't have my riding boots and really don't want it to kick back while only wearing cheap slip-on shoes.
Not sure if it is a weak coil, points or condensor. Or something else? I have a feeling that the way I am going to approach this problem is with an MZB.

Any thoughts or quick ideas?

thanks,
Mark

Right before I was ready to leave I had an idea. I had sprayed some WD-40 in the slots of the flywheel. Kicked it again and it popped. Kicked it again and it started. Wow, this bike is loud and vibrates pretty good. It didn't run very long. Then I checked spark again and there was none.

A year and a half later, I finally opened the box of 3 MZB's. Not sure which one is for the 450wr as Husqvarna 450 is not listed on the MZB website. It's no problem determining which is which as I will take some measurements when I go back into the shop. However, I do not have a spec or proceedure for setting the timing. Is the stock setting found to be the best? I know in the automotive world performance timing is a ways off of what the service manual recommends.

thanks in advance,
Mark

After some searching I found another thread concerning ignition on a '73 250 and a reply directed to
http://www.yourhusky.com/files/MK-ML_workshop_manual.pdf
For the 450wr it lists 18 degrees advance for spark. When they mention advance on piston as being 2.54 mm, it sounds like they are saying to back up the flywheel until the piston is 2.54 mm down the cylinder and that should equate to 18 degrees BTDC?
The other measurement they mentioned is 21.5 mm on the flywheel. Are they talking about making a mark ahead of TDC on the circumference of the flywheel?
Is my suspicion of proceedure correct with either method? Is there a preference on either?
This might be a bit much, I think I'd like to scribe a TDC mark on the flywheel, then scribe 18 degrees with a few degrees in either direction. Then verify with a timing light where the timing actually is. Any thoughts?

thanks,
Mark

Use a TDC gauge or a dial gauge down through the spark plug hole. You are correct in saying "back it up" by 2.54mm. The manual also gives an alternative method by measuring a distance of 21.5mm from tdc to the timing mark. This is explained better in the later manuals. Have a look at the 1978 390 workshop or owners manual. This has some good diagrams. I have not looked at the 73 one to see what it has. Just use your measurements in place of the 390 ones.

You are correct, the 2.54mm refers to the piston travel and the 21.5 would be the distance on the flywheel from TDC. The bikes are set up from HVA with both a TDC mark and the BTDC timing mark punched on the flywheel so I would say to do the same with your new ignition.

I've never used a timing light but I've seen them used in videos on Youtube. Myself, I've had good results using a dial indicator. My experience is that you don't need the timing to absolutely perfect to get the bike to run. However you will need to tweak it to get the performance and starting characteristics that you like.

On these MZB, is the only way to adjust the timing by pulling and turing the flywheel? Or, can you put a screw driver through one of the holes to adjust the base plate? Last night I started the installation. But, was feeling worse and worse in the time I was at the shop and called it quits. I caught a cold that is kicking my butt.
Anyway, I made a piston stop to find true TDC. The only problem I found is that I have no way to hold the crank in position when removing the degree wheel. If the clutch cover were off on the other side there would be a place to hold the crank stationary. I was trying to do this without the use of the dial indicator, because I don't have one that fits in the spark plug hole. However, the with the dial indicator in position, I'd be able to move back 18 degrees on the degree wheel and verify the 2.54 mm. Then if the crank position were disturbed while removing the degree wheel or installing the rotor/flywheel it would be easy to return to proper position by reading the indicator.
I guess it's time to get an indicator that mounts in the spark plug hole. Or, break the porcelin out of an old spark plug to make an indicator base...like the way I made the piston stop.

Here is the 73 on my transmission shop building bench:



The MZB parts laid out and read for installation:



My automotive degree wheel on the 450wr crank:

Not sure if too many people use the degree wheel. My thought is using the degree wheel with a piston stop will find true TDC will eliminate any possible error from piston dwell when finding tdc with just an indicator. Unless you use the indicator with the paper strip method.

if you dont have one a thread in dial indicator is very nice to have, as you are seeing

In my opinion you're splitting hairs. A half a millimeter one way or the other won't make any difference.

As nice as dial indicator equipment can be I realize that if the funds aren't available then you have got to do it another way.

Remove the tank and the spark plug. Insert a Phillips screw driver in to the plug hole and find TDC, then mark the new flywheel with a punch at the timing mark on the center case (located at the upper left hand flywheel cover screw hole).

Then measure the circumference of the stock flywheel and determine what percentage 21.4mm is of the total circumference.

Then measure the total circumference of the MZB flywheel and multiple it by the percentage determined in the prior step. This will be the distance the BTDC timing mark must be for the MZB.

To the right of the TDC mark on the MZB flywheel that you made earlier measure the determined distance and make another punch mark which will be the required 18 degrees BTDC.

Yes, it certainly looks that way.

Anyone have a part number or resource of where to get one? Otherwise, I might make one from an old spark plug.

That is a good method to employ if one were out in the field and needed to set the timing. Some people are probably pretty accurate in this method. I have the feeling I'd be atleast several degrees off one way or the other. While the bike is on the bench, I'm going to attempt to target the timing as best I can.

i can get you a number

In the photo is a Central Tools timing gauge being used on my 400CR. Mines pretty old, but they are still available, Central Tools 6491A. Kind of pricey though.

Also made a piston stop from an old spark plug as you did, 8mm bolt fit tightly through it, had to cut the bolt a couple of times until I had the length needed. Finding true top dead center with a piston stop is certainly the most accurate way. Rotated engine clockwise to stop, made mark on flywheel, then counterclockwise to stop, marked again, halfway between marks is TDC. (I think this is the same procedure you are using based on your post).

I have also used the method described by crashaholic, measured the outside diameter of the flywheel in mm, multiplied by pi (3.1415) to get the circumference, then divided by 360 degrees to get mm per degree. This is where Husqvarna gets the 21.5mm measurement before BTDC, which relates to 2.54 BTDC piston travel on your 450. Since your new flywheel is likely a different diameter, you can use this formula to determine where 18 degrees BTDC would be if not using a timing gauge.

Incidentally, the 22 degree BTDC timing mark on my 400 flywheel turned out to be 6 degrees slow when at 3.5mm BTDC piston travel (spec for 400CR 1970). Really woke the motor up with correct timing.

Good luck with the 450, still running Femsa with points on my 400.

I just installed this same powerdynamo on my '74 wr250. I printed a degree wheel printed out from online, and used an old calipers with a depth gauge down the spark plug hole (holding it steady with clamps) I ended up with 2.75mm of piston travel BTDC. This was at between 20 and 22 degrees advance using the degree wheel, I am not sure exactly because the piston pauses for a few degrees at the top. the manual says 20 degrees advance, it was set at 22 degrees by the former owner so I figure anywhere in there is ok. I have not finished the wiring yet so have not yet started the bike...

its probably pretty close at least! i think if you are going to err, err on the retarded side. easier starting, less kick back, less strain on motor. best power is fully advanced tho. you are close enough that nothing will be harmed and should start ok...i think..

I'd say Crashaholic right about splitting hairs. Sunday night, I had made a dial indicator holder out of an old spark plug. There really isn't very much piston dwell at TDC. It took very little crank rotation to send that indicator needle going the other direction. I mean I had to be pretty careful to get the needle to stop at zero. I didn't use the degree wheel to determine how much dwell there actually is, but it was less than I had expected. The 2.54 mm of advance was pretty easy to get without a metric indicator as 2.54 is equal to .100".

Here is the piston stop, indicator holer ans lengthened indicator tip I used to get the timing set.

Wow, awesome tools you've whipped up. I have a lot of admiration for riders that make their own tools.

Now I understand the dial indicator extension and the holder but what does the piston stop do?

The piston stop was for use with the degree wheel. Imagine if the piston stop was installed and as you rotate the crank the flywheel stopped at 11 o'clock. Then, then you turn back the other way, it stops at 1 o'clock. Exactly in between would be 12 o'clock and that would be TDC. It's an accurate way to find TDC.