Help me out.

I'm trying to start my bike today for the first time after rebuild *Note: I did not rebuild the motor*. '74 850 with Mikuni and Boyer. All electrics work. Have real good spark. Have compression. What I don't have is my gas tank (still at the painters) so I rigged up a huge syringe to the carb via fuel line and took the plunger out. Dumped some fuel into the syringe, it emptied into the carb, so I put some more in, then it started coming out of the overflow. So I def had fuel in the carb. Put the choke on (lever down on mikuni) started kicking. Kicked about 10 times with nothing, pulled plugs and they were dry. So I turned the ignition off and kicked a few times with the throttle open, plugs now wet. Turned on ignition and kicked a few times and got the loudest pop out of the right side exhaust (like a small caliber gun "pop"). Kicked a few more times and got a much much smaller pop at the carb and smoke out of the air filter. Did the exact same thing again a few kicks later.

I'm guessing it has to be fuel delivery. Why was gas coming out of my overflow? Does the temp gas tank (syringe) need to be sealed up better (i.e. not open to atmoshpere)?

I'd really like to get this thing going today. With all the help you've given me so far, hopefully you can help me finish.

Thanks again,
Ben

I'd first check Boyer timing and that its trigger leads are connected in correct order. Gas tank must be open to atmosphere not to create a vacuum. MIki over flow implies stuck float so give carb a few good raps before opening up.

Spark, fuel, air, timing...pretty much covers it.

have you checked the rotor timing mark is the one that corresponds to the piston coming up on compression? Its easy to get that wrong and then your timing is 180 degrees out which leads to a spark combustion in the exhaust, thus the loud pop.

Mick

Fuel out the overflow is stuck floats. The dual floats on Mikunis ride on a peg which easily gets gummed up. I'd pull the carb and remove the float bowl. Thoroughly clean the float bowl and the pegs and floats. Don't miss the hole in the float that the peg goes through.

When you have the carb clean, clean or replace the spark plugs. The stuck floats have flooded them and they are probably fuel fouled.

This happens on my cafe racer (dual Mikunis) often when it sits for any length of time.

Well, no luck fellas, she just wouldn't light up. Kicked it way more than it should have needed.

Firstly, I dropped the bowl on the carb and the floats were floating freely. I ended up having to change the height a little to get it to stop overflowing. Put it together and no more overflow. And I was still getting gas to the cylinders. So that should be fixed. Thanks.

Mick - That definitely makes sense. I would put the choke on, kick it through twice, turn on the key and kick like 10 times and get nothing. Take the choke off kick it a few times and get the real loud pop out of the exhaust. Really loud. Then start over again. I know it was flooding but I didn't know what else to do.

To time, I pulled the inlet tappet cover and turned the rear wheel while in 4th gear. I watched the left intake valve go down and then once it started coming up, I watched the degree scale in the primary inspection hole for the stator mark to line up with 30 degrees (I know boyer calls for 31 degrees). Once lined up, I went over to the timing side and put the rotor on (I already pulled it off before setting the degrees) with the magnets in line with the norton logo. Put the center bolt in and tightened up. Then put the plastic stator plate on, looked through the hole on the left and centered it on the magnet. Went back over to check out the primary side to make sure nothing had moved. To my knowledge, the timing should be correct, unless I've somehow used the wrong mark to set the degrees BTDC. Honestly, I really hope its something as simple as that. The bike ran before I tore it down, it should run now.

I was getting a nice fat blue spark on brand new AP63 plugs that were gapped to .025 per the manual. I was definitely getting gas, plugs were wet every time I pulled them to dry them. I also definitely have compression.

Let me know what you think.

Thanks for the help everybody.

Ben

So, I guess what I can do to be certain I'm using the correct timing mark is to put a rod in the spark plug hole and make sure the piston is coming up when the inlet valve for that cylinder is closing. Correct? Then, whatever mark is going by the degree indicator at that time is the correct mark.

Just looking for verification of my timing method and any suggestions are definitely welcome!

Thanks,
Ben

I think the correct timing mark lines up with keyway on the rotor,If I remember right. But you cant see it unless you take the rotor off. I mark that line on the rotor with red fingernail polish.

Phil

It sounds like you've timed to the wrong mark on the rotor.

As already mentioned but bears repeating: If you take the spark plug out and put a pencil down the plug hole and determine the piston is rising, then start looking for you BTDC mark,you will most likely find you're timed to the wrong mark.

HTH

BEWARE breakable things in plug hole as piston rise more sideways to it than push. If ya break wood off inside you can float it by flooding with gas or diesel with piston up near top. Suck most out via syringe. Both pistons move the same so only slack valve lash lets ya know which is which.

As Kenny mentions, I lost most a week having timed points to wrong jug going by push off of finger in hole as piston rose, switched trigger leads and got going.
Also electronic ign. must have their trigger leaded in right order too or can act just like yours, if they are still constantly conducting, not fractured copper under insulation.

To clairify Hobot,

You're saying if I have timed it to the incorrect mark, it should be off 180 degrees and therefore I could swap the spark plug leads and it would work (the bike would run)? I understand that the correct way to fix my problem is to reset the timing rotor, which I will do, but I'm just trying to understand what's happening so I will be able to troubleshoot these problems better in the future. Plus, I don't think my spark plug leads would reach that far.

Thanks again,

Ben

Wet plugs usually point to poor or no spark, or way too much fuel.
Once you've confirmed everything should be as it should and it still won't start.

When you're kicking it over try to follow through and get two compressions

Try; Fuel and ignition off, plugs out and full throttle kick it over half a dozen times.
Clean and dry the plugs heat them up if need be refit them and repeat. Then with fuel and ignition on, no choke no flooding, try again with very little or no throttle and see if it'll respond. It might just fire up and stop, if so give it a bit of choke.


Best of luck,

Cash

FWIW,, you do have a fully charged battery right??? Mine will do funney things if it's even a tad bit low.

Thanks for the tips guys,

Battery reads 12.44 volts and I have it on the trickle charger until I can get back to it.

I won't be able to try anything until Saturday as my bike is an hour and half away at my Dad's work shop.

Ben

Check your wiring orientation on the pickup plate. If the two leads are reversed it will result in the effects that you describe. Do the piston location previously described and the pickup magnet should be pointing to the three oclock position for correct timing.

Just to clarify, since it seems that you have electronic ignition both plugs should fire at the same time - one is a wasted spark - so swapping plug leads will not make any difference. The suggestion is that you might be 180 Degrees out of sync, ie. that the plugs are firing at the bottom of the piston stroke rather than at the top. Holmeslice's pencil method will quickly indicate whether you are in the ball-park, just keep lifting the pencil out as the piston comes up to avoid breaking it off inside.

Since you are using electronic ignition, your coils should be 6 Volt units, as they are connected in series. With points ignition you have two separate coil feeds and no wasted spark, so the coils should in this instance be 12 Volt units and in this configuration it is possible to time the bike 360 degrees out, in which case swapping plug leads could solve the problem.

dave M - Thank you. Your response is what I was looking for. Now I understand what is actually happening. I really hope this is the case and I can just re-time to the correct mark and have it fire.

Honestly, I should've been able to figure this out on my own. I've read about how to troubleshoot this type of stuff before, just never actually done it. I think I was just really dissapointed that I couldn't get it to run and that clouded my judgement.

I'm pretty confindent I can get it going now that I understand it better.

Once again, I can't thank you guys enough. You can bet I'll let everyone know when I get it going this weekend. Maybe some newer pictures tonight if I get a chance.

Thanks!
Ben

*Edit - The PO rode this bike for years with the current boyer system with no problems. I have not changed anything with the ignition system at all, so there's no chance of incorrect coils or anything like that.

It's probably not your current problem but check the coils anyway, either 6V or 12V is printed on the opposite end of the coil to the HT lead, it will run with 12V coils but much better with 6V units and they are cheap to change if this is the case. Good luck

Will do Dave. Can't wait to get back to it now!

Ben

one other thing I've seen mentioned in other threads, but not here- don't assume your timing scale in the cover is correct
not really related to your problem, but more a fyi