Rebuilt the engine, now it won't start *Fixed!

[stormi]

Hi All,

We rebuilt Dita's engine, as it turned out, she didn't need a camchain, just a really good cleanup.  She had tons of carbon deposits on the valves.  The chain was as new, which sucks, cos now I have parts around that I don't need. (that's what I get for listening to the Dealer's diagnosis)

Anyway, after reassembling everything,.. she does as she did last spring, cranks and cranks and cranks, but doesn't seem to want to start.  

I have checked for spark.  It sparks, having never tested for spark before, I found the dancing about that the spark did to be kind of strange, but there was definite spark.

I would really like to rule out compression ( since the top end was just freshened up - rings, cylinders, pistons and valves in spec...) but I will be picking up a compression tester this evening to make sure I don't overlook something I shouldn't.

So,.. In my mind... this leaves only fuel, no?  

This year, the carbs were stored in a plastic bucket, off the bike, in the basement ( since she was torn down for the engine work) therefore,.. she really couldn't have had them more drained.

There is currently gas in the bowls ( I can tell this by turning the drain screws, and having gas drip out) This seems to rule out the petcock and fuellines, correct?

Last night, we tried to start her, after finally getting her back together, and I apparently had left the drain screws open   , so there was gas everywhere.  We tightened those up and tried to start her.  No go, and she smelled flooded.  We gave her the night to "air out", but I got nothing better out of her this morning when I tried to start her.  

Why should I have to take the carbs apart yearly to make them operate?  I know of people that just park their bikes, and fire them up in the spring, are the bandit's carbs really that finicky? Or am I missing something else?

I really want to get this sorted, so we can get the dirtbikes ready for the year, and have no more torn down bikes in the shed.  

Thanks

[interfuse]

Got the right firing order?

Carbs should be okay. To rule them out you could try starting fluid.

[erik]

After I did the valve shims on my bandit, I had to use a makeshift fuel tank with no vacuum fuel valve so that enough fuel got to the carbs. With just the tank, I think the carbs weren't filling up enough, I ended up flattening the battery cranking it over.
At least I think that's what the problem was.

[Krautwagen]

You can accomplish the same effect by removing the screw in the petcock and turning it past reserve, otherwise known as 'prime'.

Sounds like it's flooded to say the least.  Airing them out doesn't always work.  Sometimes you have to pull the plugs and dry them off or apply some heat.  If they look wet, dry them off and keep trying.

Engines can take some time to fire after a rebuild.  Are you sure you got the timing correct?  Always double and triple check valve timing and ignition timing when reassembling.

[Red01]

One more thing to add to these fine suggestions...

Is the gas in the tank fresh?

Sure, the carbs were dry while apart, but if you left the old gas in the tank all this time, it will have still gone bad. Bad enough to not want to burn.

[stormi]

Got the right firing order?

Carbs should be okay. To rule them out you could try starting fluid.

Yep,.. the firing order is right.   Starting fluid.  i likely would have picked some of that up if we hadn't been in small town alberta at 9pm when I read that. :)

[stormi]

You can accomplish the same effect by removing the screw in the petcock and turning it past reserve, otherwise known as 'prime'.

Sounds like it's flooded to say the least.  Airing them out doesn't always work.  Sometimes you have to pull the plugs and dry them off or apply some heat.  If they look wet, dry them off and keep trying.

Engines can take some time to fire after a rebuild.  Are you sure you got the timing correct?  Always double and triple check valve timing and ignition timing when reassembling.

We did prime.  I forgot to mention that.  

The plugs were dry,... I checked them when I was checking for spark.  No compression test yet, since the compression tester fit all spark plugs but those. *sigh* oh well, back into town for a different tester.

The other half swears the timing and valve timing are correct.  

I have heard in various places that an newly assembled engine takes time to fire,.. why is this?  (Being brand new to dissecting engines myself)

[stormi]

One more thing to add to these fine suggestions...

Is the gas in the tank fresh?

Sure, the carbs were dry while apart, but if you left the old gas in the tank all this time, it will have still gone bad. Bad enough to not want to burn.

It's a mix of fresh ethanol blend and the old ethanol.  about half and half.  Should I just drain it all and put it in the lawnmower and start fresh?

[Red01]

Yes! And if you can get premium gas without ethanol, that would be best.

[stormi]

Yes! And if you can get premium gas without ethanol, that would be best.

How come without Ethanol?

[Krautwagen]

Ethanol fuels have less resistance to detonation and less thermal capacity.  These 'high performance' engines are more suceptable to detonation (knocking) due to the higher rev's and higher compression than you standard car engine.  Higher octane fuels prevent engine damage by prevent detonation.

[Red01]

Ethanol fuels have less resistance to detonation and less thermal capacity.  These 'high performance' engines are more suceptable to detonation (knocking) due to the higher rev's and higher compression than you standard car engine.  Higher octane fuels prevent engine damage by prevent detonation.

What he said... in a nutshell, it'll run better in both performance and economy on pure gasoline than it will on a blended fuel.

Also, ethanol is known to cause erosion in the tiny passages of carbs when used over the long haul. It can also have an effect on rubber parts exposed to the fuel if the system wasn't designed for it. Chances are as old as your B4 is, it wasn't designed to handle it.

As a side note, I will only used ethanol laced fuel if I have no other choice.

[stormi]

Alright,.. check,.. no more ethanol fuels.  We (ok, the other half) took the carbs apart, since they were off anyway,.. and found sand (?!?!) in the bottom of the bowls!  So,.. I have no idea how that got there, but he's going to clean this all out, and reassemble, and we're going to try again.  In retrospect,.. it's a good thing she didn't start.

I don't know yet if this is the root cause, but it certainly couldn't be helping.

[stormi]

Ok, cleaned out the carbs - no more sand.

Also found that the choke cable had been re-routed incorrectly, and the throttle didn't have full throw, so I'm guessing that she was getting a little fuel when she shouldn't be.  (My fault, I didn't remember how it was supposed to be set up from when I took it apart in October.)

We disconnected the throttle cable, and sprayed a little WD40 into the carb intakes, and she began to fire,.. but we couldn't keep her running.  No matter how hard we tugged on the throttle cable.  Ok,.. now let's reconnect the throttle cable - correctly this time - and try that.  

Yay!!! she fired up!  She even idled with a little turn of the idle screw.

Took her for a really quick ride, and promptly broke the Gear shift link Rod.  *sigh* Oh well,.. that should be a quick fix.

The spark seems a little weak on 1 and 4, so I might look into a new coil for her, or see if Iridium plugs (did wonders for my KTM) will help her out any, or both.  Other than that, she seems pretty happy.  

We didn't change the camchain after all, she was just -really- carbonned up.  And while we were in there, we changed the front sprocket, to gear her a little better on the highway.  It should be fun to see how she feels once the GS link rod is replaced.

Tomorrow, wash and wax.  I promised her that she'd get that once she started for us.  I intend to keep the promise.

Damn! I'm almost giddy listening to her start up after so long.  

Thanks to everyone for all the help and suggestions!

[erik]

Good to hear you got it going :)