Follow up question on 1.3 rocker....beyond frustrated

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blockdoc

New Member
#1
#1
Hiya guys,
I am a treasure trove of questions

As I mentioned in the previous thread, my son and I built a modified predator engine in anticipation of putting it on the Azusa.
Engine worked GREAT, started easily with one pull, and throttle worked flawlessly. Started it up and let it run at least 5 or six times. The mods at this time were:

Arc Stnd Rod
Arc Billet FLywheel (gap at .055 or so per Arc recs)
14cc head (ported and polished)
Mod2 Cam
Stainless steel valves (standard rockers)
Honda 0.625 Carb (NR Racing)
Header
Autolite AR3910x sparky

I ordered and installed at 1.3 stamped rocker from Arc along with the appropriate guide plate...I CHANGED NOTHING ELSE


Set valve lash as noted above (currently pretty close to 0 degrees cold at TDC)

NOW,
Engine is very difficult to start (in fact, I only got it to start once after MANY pulls and sore hand) Revved once and died.
It "pops" every third or fourth pull, I smell gasoline (smells rich), and sometimes hear a pop and see exhaust puffing out of Carbeurator.

I pulled the valve cover, rechecked lash. Rechecked coil gap. There is a visible spark from the spark plug. I smell gas so am doubtful it is a fuel problem.

I am stumped. and VERY frustrated. About to pull the head....just to DO something. Not really sure what I am looking for.

The only thing that has changed is the rocker. Unless this is a "red herring" as they say.


Help!

Thanks

Brian
 
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David wulf

David wulf

#2
#2
Hey it sounds like the timing is off , but I don't know . It won't take 20 min to put the stock rockers back on and see if that fixes it , it's worth a try .
 
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blockdoc

New Member
#3
#3
David wulf said:
Hey it sounds like the timing is off , but I don't know . It won't take 20 min to put the stock rockers back on and see if that fixes it , it's worth a try .
Click to expand...
Thanks for the input!

I was able to get it started by putting in new stock spark plug. It still almost ripped my hand off when starting lol.

I suspect I am running rich and fouling plugs.

Should I put a smaller jet in?

Thanks
 
OND

OND

#4
#4
Hey doc, that Mod2 cam has a ton of duration..correct ? and now you've added 1.3 ratio rockers ? It might break your arm ! Just sayin...
 
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blockdoc

New Member
#5
#5
Is that it????? How does long duration affect the dnagerous pull back?

Perhaps I should take the damned thing off. Its almost unmanageable at this point....definitely not possible for my son to start it. Im a pretty solid guy at 215 and I can barely start it.

I'd bet the 1.3 rocker is barely an incremental gain anyways. We have WAY too much power as is LOL
 
OND

OND

#6
#6
Just might not be very user friendly at this point ..I agree...:thumbsup:

It would be great for a open engine in a racing kart or mini bike...but I would want to use a racing starter to start it.
 
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bdomit01

New Member
#7
#7
I pull start my big bore stroker at 14:1 compression and a much bigger cam almost as easy as easy as it was stock... If you're having that much trouble starting it then either the timing is off or the lash is still incorrect and not engaging the compression release. I've had both of those happen multiple times with very similar symptoms.
 
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durandbagwell86

Member
#8
#8
Make sure the rocker arms sit all the way on the stud and move correctly. I bought a set of reinforced rockers and they were made wrong. I put some champions on and it worked perfect. Also try adjusting turning it slightly past tdc.
 
Prowler08

Prowler08

New Member
#11
#11
if I remember correctly... I had to put a small washer under the intake stud to get enough adjustment on the intake side using that combo...
Also make sure your pushrods are not too long using that 14cc head...
We ran into a problem on one engine that the deck height was slightly shorter than the others, causing geometry issues, and a similar problem you are experiencing.... Had to use 5.175 rods instead of stock rods...

That NR carb. Will make it run very rich... Especially at idle...
Try using just the stock carb till you get things running smoothly, then put the NR carb. On...
 
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blockdoc

New Member
#13
#13
kruger said:
this sounds like a valve lash problem, especially since exhaust is coming out of carb.
Click to expand...
Thanks you two. Good points.

Alls I can say is that I checked, rechecked and rechecked valve lash multiple times with the 1.3 rocker on. Even at "zero", the problem presisted

How would I know if there is any geometry problem with the 1.3 set up?. It runs fine with stock rockers. Is there any way to check?
 
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blockdoc

New Member
#14
#14
I noticed that about the NR carb........smells rich and soots up the sparkies....mostly at idle.

Is it worth rejetting? Or should I just wait until we can actually run the thing under load and rpms?

Thanks so much for the input
 
Prowler08

Prowler08

New Member
#15
#15
The carb is set up to race... Defiantly not to idle or putt around with...

Check geometry by taking marker and colour the top of the lash cap and see where it makes contact with the rocker and cap...
Should be in the middle...
 
minibikin'

minibikin'

Sho-nuff
#16
#16
Prowler08 said:
The carb is set up to race... Defiantly not to idle or putt around with...

Check geometry by taking marker and colour the top of the lash cap and see where it makes contact with the rocker and cap...
Should be in the middle...
Click to expand...
It should be in the middle at half lift...


Sent from my Texas Instruments Speak and Spell...[emoji2]
 
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