Topic: No start condition after rebuild- NOW IT RUNS!

[Trav-i]

Hey gang,

As the title says I've got a conundrum here.  I have recently gotten around to finishing up a top end rebuild of the engine for my 750.  Life and a lack of free time caused the rebuild to drag out longer than it should have.  In summary it is a 1975 super sport engine.  The original intent was to just do a head gasket and cam tower pucks, and valve stem seals to freshen it up and stop all of the oil leaks it had.  Well once I took the head off I saw some light damage to cylinders and cam chain tensioner, so I decided to pull the cylinders to replace the tensioner and hone the cylinders.  So fast forward to now.  The engine is done, fresh piston rings along with fresh cylinder hone, new Honda cam chain tension and rollers, fresh head gasket, pucks, and stem seals.  The camshaft was put back in per the Honda manual notch up and hash marks level with the holders.  I adjusted the valves per the book before I put the valve cover on.

Now here is my issue.  After installing the engine and getting everything hooked back up I have a no start situation.  The bike itself is a 1978 super sport.  I adjusted the points per the book and set the base timing by test light.  The carbs are the original 78 PD42b.  I have cleaned them well and I know in the past they have given little trouble.  The engine spins over nicely no issues there (The batter is new and always on a battery maintainer charger) but, I am left with the occasional pop from the exhaust and the engine makes no effort to start or run.  I checked spark condition and it seemed weaker than it should be and since the coils are original and high tension leads were in rough shape I ordered new coils and caps.  I put them on last night there is a nice improvement in spark quality but still only an occasional pop from the exhaust.  I suspect it may be a timing issue of some sort.  Gonna back over everything today if the day allows for it.

There were no running issues with the bike when I pulled the engine to fix the leaks.

Now it's time for fresh eyes and opinions on what's going on.  I suspect I am missing something simple but, having stared at the bike for the last few days I may be missing the forest for the trees.  I am always open to any information or opinions y'all have on what the problem may be.  I have no problem admitting when I mess up.  I just want to get my old Honda up and running again, the GL1500 is fun but it's big and I want my smaller bike back too.

Thanks everyone.

Travis

[69cb750]

All you need is fuel, compression ignition.
Verify points open at "F" mark.
Spay three shots of gas into #4 spark plug hole with spray can, install plug.
Report back here.

[bryanj]

I think you will find pilot jets and/or passages blocked. Did you pull out the pressed in pilots?

[robvangulik]

Advancer 180 degrees out of sync?

[Trav-i]

To answer y'alls questions, I took the advancer off lubed, checked operation, and reinstalled it with the dowel in the hole.  And I did indeed pull the slow jets, all passages we sprayed with cleaner and compressed air.

[Tim2005]

After it has spun over a bit are the plugs getting wet?

[Trav-i]

Plugs are wet, I can smell fuel in the exhaust.

[Trav-i]

For the sake of checking and verifying I went out and popped the valve cover enough to see the end of the camshaft.  I was able to verify that the cam is timed as it should be.  I did notice at TDC #1 the intake valve is a little tight.  So I will be going back through the valve adjustment on Tuesday and see if I have any other valves that need a readjustment.

[seanbarney41]

Travi...if you had thr advancer apart, it is possible you put the cam back on 180 degrees out.  There is a tiny dot on the cam that should face the tec/ nippon denso logo.  It is not possible to install the advancer incorrectly, just the cam.

[Trav-i]

Travi...if you had thr advancer apart, it is possible you put the cam back on 180 degrees out.  There is a tiny dot on the cam that should face the tec/ nippon denso logo.  It is not possible to install the advancer incorrectly, just the cam.

I took a good look at the advancer a day or 2 ago.  It doesn't appear to have ever been apart.  I know I have not ever taken it apart, it has always worked as it should.  The day I pulled the engine I ran it for a short while just to make sure all was good before I took it out.  I put a lot of miles on it since I've had it and it has given very little trouble.  This is out of character for it.

[seanbarney41]

OK, misunderstood when you said you took the advancer off and lubed...generally that involves taking it apart

[RAFster122s]

Not a kill switch situation because you are getting spark. Spark plugs all being bad is unlikely, since we are hearing reports of bad plugs out of the box that either simply don't work or don't work under compression. All plugs are getting spark, right, or at least check that both coils are working correctly.

You say you have gas, so that leaves compression...

[low-side]

I hate when some problem like this has me chasing my tail, you have my sympathies.  Any chance the coils are switched?  It's unlikely given everything else you've checked on, but it would act just like that.

[Trav-i]

After checking the cam yesterday I set the engine to run the valves again and noticed that at TDC #1, cylinder #1's intake valve is tight indicating it has pressure on it.  I know when I first adjusted the valves the engine was out of the frame and the valve cover was off, so I just visually watched the cam until I saw 1 and 4 roll on to the bottom side of the cam for compression then adjusted the valves.  I didn't keep an eye on the timing marks on the advancer.  So I suspect the valve adjustment is going to be off.  That may be causing some valves to be open or closed when they are not supposed to be.  I'll check that tomorrow.

The coils are new along with the caps and plugs.  They seem to working as they should.  Points are clean and adjusted per the manual.  And sorry for the confusion about the adjuster, yeah I just slid it off the shaft confirmed operation and oiled it.  No disassembly was needed.  I'm hoping my potentially goofed up adjustment is the problem.

[RAFster122s]

Likely your problem... hope it is the case. Going through valve adjustment again and maybe compression test after before you reinstall the plugs is a good idea. Numbers on fresh built motor won’t be normal but will tell you if there is a problem. After break-in they will all even out and come up to their best numbers.

[Trav-i]

I hope the valve adjustment is the issue.  I really don't feel like pulling the engine again.  I know that after I put the cylinders back on I rotated the crank a few times just make sure it moved freely and left no ring marks.  After several revolutions I did not notice any grooves or damage from a out of place ring.  It spins over freely with no binding. 

Here's to hoping I don't have to pull the engine again.

[CaptFatCat]

I have had this issue a few times. First I make sure the battery has a good full charge then I proceed with an old trick my Dad taught me years ago. Cover one carb intake with the palm of your hand tightly and turn it over.  Varooom bah bah!
He called this a force choke, it forces the 1 carb to suck fuel into the cylinder and fire without flooding the other 3.
works every time for me on a fresh build.

[Trav-i]

I have had this issue a few times. First I make sure the battery has a good full charge then I proceed with an old trick my Dad taught me years ago. Cover one carb intake with the palm of your hand tightly and turn it over.  Varooom bah bah!
He called this a force choke, it forces the 1 carb to suck fuel into the cylinder and fire without flooding the other 3.
works every time for me on a fresh build.

Might have to give that a try tomorrow.

[madmtnmotors]

Sounds like yellow/blue leads from points to coils are switched...

I've done it!

[Trav-i]

Well, I decided I throw out a quick update as I have had a chance to work on the old Honda this morning.  I readjusted all of the valves this morning.  They needed it bad!  Every one of them was too tight, I watched valve movement on several of them when I backed them off.  And I know what I did wrong.  When I initially adjusted them I just watched the camshaft lobes and adjusted the valves based on lobe position not actual timing position.  I guess that left everything out of time just enough.

I put the tank back on and spun the engine over and it sounded just as it should.  No more popping or backfiring.  I just need to replace the ACC pump circuit o-ring on #2 float bowl and I suspect it will be running by the end of the day.

Lesson learned today, follow the directions in the book and most of all pay attention to the small details!  LOL!

Travis

[RAFster122s]

Great news! Don't understand why you would need to pull the engine if you need to do the valve adjustment. Normally just pulling the inspection caps gives you enough room to adjust the valve. Or, did I misunderstand your comment?

[Trav-i]

RAF122S I had no plans to pull the engine for a valve adjustment.  I was just saying that I had adjusted them during rebuild while the engine was out of the frame.  I did the readjustment via the valve cover holes.

After finishing the valves I replaced the offending o-ring with the one that had been in the ACC pump circuit and that started working as it should.  I hit the starter button and BOOM it started!  Although it was only running on cylinders 1 and 4.  That took some extra time to figure out.  That ended up being a simple fix.  The feeler gauge I used on the points had some rust on it and it left enough on the pads of the 2-3 point assembly that it stopped the arc.  Cleaned the rust and cylinders 2 and 3 started firing.

It runs great!  It took entirely too long to get to this point.  I just need to do a shake down ride or 2 and then sync the carbs, then it's time ride!

[jonda500]

the timing position is used to know the lobes are in the correct position (facing down away from the rocker arm) when you can't see them - I don't understand how you could get it wrong when you can see them and visually turn them downwards! (never get to do this on the smaller SOHC4's as the rockers and rocker shafts are in the rocker cover)
John

[Trav-i]

the timing position is used to know the lobes are in the correct position (facing down away from the rocker arm) when you can't see them - I don't understand how you could get it wrong when you can see them and visually turn them downwards! (never get to do this on the smaller SOHC4's as the rockers and rocker shafts are in the rocker cover)
John

John

It wasn't that I missed or didn't pay attention to cam lobe position.  That's actually how I did the adjustment, just eyeballed the lobe position.  I had forgotten to pay attention to the timing marks on the advancer.  Missing that small critical small step caused a lot of headache for me.

[jonda500]

the timing position is used to know the lobes are in the correct position (facing down away from the rocker arm) when you can't see them - I don't understand how you could get it wrong when you can see them and visually turn them downwards! (never get to do this on the smaller SOHC4's as the rockers and rocker shafts are in the rocker cover)
John

John

It wasn't that I missed or didn't pay attention to cam lobe position.  That's actually how I did the adjustment, just eyeballed the lobe position.  I had forgotten to pay attention to the timing marks on the advancer.  Missing that small critical small step caused a lot of headache for me.

errr my point is that you don't even need to look at the timing marks at all if you can see the camshaft lobes as all that matters is having the lobe pointing away from the rocker arm that you are adjusting. Sorry if I am misunderstanding you,
John