The VI bobber now runs… but not well.

Halftwist

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We’ll just about have this whip buttoned up.

First Fire: Fired it up started second kick, single choke on. The motor seemed to want run off, and there was a fair amount of popping. This is leading me to believe it’s lean. Let it run 30 seconds. Shut down. Felt engine and headers for temperature. Left side hot, right side warm. Pulled plugs, left side looked fine maybe lean. Right side was slightly wet with fuel and appeared to not have fired. Readjusted the valves. Check to to make sure I had oil flow through out. Pulled carbs, cleaned again, checked plumbing and jets.

2nd Fire. No change in running condition.

Was wondering If you guys had any ideas. I will post all details of complete engine rebuild, ignition, and carbs so you have all info if there is any interest
 

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RustiePyles

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What kind of ignition? Points or Electronic? OEM or aftermarket? Looks like BS38 carbs, have you synchronized them? Did you set your float level's? Have you matched your air/fuel screws? Where are your air fuel screws set to right now?
 

Halftwist

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Bottom end:
Hot tanked
New crank
New rods
New wrist pins
New pistons
New rings
Honed cylinders
New gaskets

Heads:
Hot tank cleaned
Decked and lapped valve seats
New valves
Cam was in spec
New timing chain
New gaskets
Cam chain tensioner checked after each run.
Valves checked and set before and after each run. .002 intake .004 exhaust

Ignition:
HHB CDI complete system. Newest version
Hugh’s recommended capacitor, no battery
Hughes supplied NGK plugs and leads.
Set to base line timing on the pick up adjustment per instructions.

Exhaust:
Stock header
28 inches pipe added to end of header.
Inserted a piece sheet metal into a slot cut halfway through pipe,4 inches in from end of pipe, and tacked then trimmed smooth and brazed it solid. Repeated same thing 4 inches further up pipe coming from the other side. New exhaust gasket.

Fuel:
New tank treated with kreem tank liner kit
New pet cock with screen. Non vacuum type
New fuel lines and tee
103 octane non ethanol fuel


Intake:
Stock manifolds( I know they are not the best for free hanging carbs, have ordered some new ones, however checked carefully for splits crack holes and they are in working order) they have no vacuum holes or barbs.
New manifold gasket’s
UNI closed end air pods

Carbs:
Stock BS38s
Cleaned soaked blown out with compressor and carb cleaner.
Basic stock rebuild( gaskets, jets, needles,clips,float plunger)
Floats tested for leaks
42.5 pilot
130 main
Needle 4th slot
Air screw out 2.5 turns
Float height 25mm on the money.
Mr. miyagi welding rod carb sync. Close but not perfect I’m sure. Waiting on vacuum gauge

Lots of other work and mods done will do a full build progression w pictures when she’s done. This is the pertinent info for my problem right now. Let me know if you need any other info. Thanks guys!
 
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Halftwist

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Went through both carbs again. Checked vacuum. Lifted the slide and held large air hole on top of inlet closed and the slides just barely closed very slowly. Double check with round stock the balance between carbs butterflies. Went through choke.

Hooked up timing light.

Fired engine. Same running condition as first post.

Should the engine be firing at the advance mark at an idle? Because that’s where it’s strobing. And it’s steady no bouncing.
 

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RustiePyles

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Went through both carbs again. Checked vacuum. Lifted the slide and held large air hole on top of inlet closed and the slides just barely closed very slowly. Double check with round stock the balance between carbs butterflies. Went through choke.

Hooked up timing light.

Fired engine. Same running condition as first post.

Should the engine be firing at the advance mark at an idle? Because that’s where it’s strobing. And it’s steady no bouncing.

No it should be advanced under throttle. It should be on fire at idle.
 

Halftwist

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I put some 45 pilots in working off the theory that if too lean therefore hunting. It seemed to slow the idle down quite a bit. I warmed it up a bit and readjusted cam chain so pin is flush with bolt head. Timing light still shows firing on advance. Left side still warming up more and has a throatier sound than the cooler right side. There is no way it’s idling over 1500 rpm’s right now. While I realize this is still to fast shouldn’t it be inching towards the fire mark?? Should I start thinking faulty CDI box just yet or keep going down the carb rabbit hole?
 

RustiePyles

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Halftwist

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You can probably rent a tach/dwell meter from an auto parts store. Should Idle around 1100rpm. Or buy a clip on tach.

https://www.amazon.com/Jayron-Induc...ocphy=9023257&hvtargid=pla-558377021894&psc=1
I have a tach dwell meter but it’s for 8 cylinders. Not sure what the math would be on that. x4=2?
You can probably rent a tach/dwell meter from an auto parts store. Should Idle around 1100rpm. Or buy a clip on tach.

https://www.amazon.com/Jayron-Induc...ocphy=9023257&hvtargid=pla-558377021894&psc=1
 

RustiePyles

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I have a tach dwell meter but it’s for 8 cylinders. Not sure what the math would be on that. x4=2?
It would be 1/4 the value of a 4cyl since it fires both cylinders every 360dgrees. For a true value you would need one with a single cylinder setting.
 

Halftwist

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It would be 1/4 the value of a 4cyl since it fires both cylinders every 360dgrees. For a true value you would need one with a single cylinder setting.
Yea I wondered that seeing as there’s only one coil and it fires on the exhaust stroke as well. I pulled the right side plug and grounded it to frame and it’s firing hot so it must be a carb issue… or timing
 

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Does it still have the mechanical timing advance? If so, it could possibly be weak springs on the advance mechanism. This would allow some advance at lower speeds? If the advance is taken care of by your replacement ignition, ignore this post.
 

Halftwist

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Halftwist

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Does it still have the mechanical timing advance? If so, it could possibly be weak springs on the advance mechanism. This would allow some advance at lower speeds? If the advance is taken care of by your replacement ignition, ignore this post.
No all of that is gone. The points, and the bob weight advance
 

Halftwist

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Ok I did some work double checking my timing making sure that’s not my culprit. Built one of gggarys sliding piston stops. I like it for valve friendliness. I had TDC dead on.
Now two questions:
#1. Does this pin hole on the advance side of camshaft line up with the TDC notch on the cam gear on a ‘74( if memory serves me correctly it does but I assembled the motor a year ago so I may be wrong)

#2. If the notch and the pin hole do line up, is the cam close enough to center as the picture shows if the crank is at TDC. It almost appears I’m back a tooth😕
 

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