J30a V6 Bike Carby Engine Build

[Paul]

all of a sudden the engine came alive comparatively speaking- revved through 6200 rpm wot and just begged to be given the handle. This was an improvement of over 700 rpm and made all the difference.

Going from 5500 to 6200, is a 43% increase in HP (as long as your blades are all fully 'hooked up').  Great achievement.

[Jeff B]

Great result! 6200rpm is what I'm getting on my j30a6, I thought the older J30s made peak power at around 5500rpm? Might need a bit more pitch to make the most of torque ?

[Warwick Marflitt]

Awesome Kakapo. That fat Ignition spark with the vtec has put the bark into it. It was always going to be loud once you got it sorted mate!!! You'll need a fancy air box to quieten it down to talking levels.... 

https://www.google.com/search?q=IDA+carburettor+air+box&client=firefox-b-d&tbm=isch&source=iu&ictx=1&fir=cPX7M3E3dOePFM%252Cwq1hWzX2OZaulM%252C_&vet=1&usg=AI4_-kRzkLFpc_tk7bfWoubefh281t28Pg&sa=X&ved=2ahUKEwjQr7bsi9XuAhUBwTgGHc_nBQsQ9QF6BAgEEAE
 

[Jeff B]

I tested a v tec solenoid load once and it only drew about 800ma (0.8 of an amp) so was easily switch6straigjt from ECU. That was a 2 wire solenoid.
The 1 wire solenoid had me stumped as needed 12v to activate and ecu switched to ground...so I used a relay to switch it.

[Kakapo76]

The first one we installed died after 2 minutes of use. There's no protection for the collapsing field if it's not run through an ecu. I probably wouldn't have had this issue except it's a frankenstein motor on a dizzy and carbs so the signal is coming to the switch directly from the coil. The relay. Buffers it nicely so I think it's all good now. You are right, took a bit of jiggery pokery to work out the ground on the 1 wire solenoid.

[Paul]

If there's a collapsing magnetic field in it, then putting a reverse-direction diode across the component, protects the rest of the circuit, and allows the diode to short ciruit/shunt the collapsing current safely.  Just a thought.

[Kakapo76]

Hi Paul,

That's exactly how most ecu's deal with it- was simple to run a relay, I like relays overall. I am going to play with the cooked unit and see if I can resurrect it and do what you suggest.

[Paul]

Using a relay is fine, but it won't solve the issue long term - you'll just end up burning/welding the contacts in the relay with the arc.  Using a relay and diode, should work well though.

[Warwick Marflitt]

A snubber circuit or flyback diode is what you need. Here's how it works

https://www.douglaskrantz.com/ElecFlybackDiode.html
 Narva,Hella,Bosch and other relay manufacturers all make relays with internal diode. Plug and play really. Put a diode accross the VVT coil in the correct direction. The relays contacts and chance of inductive/radio/electrical interference are greatly reduced...
The diode sends any generated reverse current to ground snubbing out any interference...

[Kakapo76]

Great result! 6200rpm is what I'm getting on my j30a6, I thought the older J30s made peak power at around 5500rpm? Might need a bit more pitch to make the most of torque ?

 This is why we need that dyno testing, I am curious if the torque curve holds on longer than it initially appears- maybe its flatter and the torque at 6000 plus is still similar to the peak number?

[Kakapo76]

I think I am cursed.

Threw a rod out the side of the block today. At this point, I am not sure what caused it. Water temps were rock solid at 85 deg c, oil temp was 90 deg c, I richened up the jets and the engine exhaust temps seemed totally fine- 7 mins up the Waimak I noticed an odd noise- slowed down to a crawl it's knocking like mad- oil pressure was very low, gave it a bit of a throttle blip- oil pressure picked up instantly, tried to get back on the plane downstream and the rod let go.

5 hours to get a tow, very unhappy wife, this is doing my head in.

I am using the factory sump- I have not changed the oil pickup- I had plenty of oil in it cold- I can only assume the pickup was sucking air under full acceleration upriver and I have spun a crank bearing, the hole in the block is dead centre just above the sump.

If anyone has any thoughts on how to prevent this from happening again I am all ears. I will post pics once I tear the engine down.

It was going so well!   

[JohnR]

My money is on afr.

[Warwick Marflitt]

Manifold gasket leak? Closing throttle at High revs and sudden vacuum pulling a gasket in? Check the plugs color? Although leaning out shouldn't effect oil pressure. Was it detonating maybe? Strip it and have a good look....
Can vvt increase airflow beyond the carburetor jets or fuel pumps ability to supply enough fuel? The joys of experimental  development aren't without challenge....

[Jeff B]

Although the fuel mixture might not be perfect, it's not common to throw a rod because of it...normally burn a piston or valve.
Too much advance will do it (pinking), knocking will hammer the big end shells, end of shell curls over and scrapes the oil off journal
 
Most likely oil problem? How much of an angle you on while crawling onto plane? Cant be worse than my j30 playing around doing wheelies? 
I haven't even had the sump off a j series, I'm guessing the pickup is close to front of sump?
You haven't plumbed up a remote oil filter or cooler backwards have you?

[Ross Goldsack - JBNZ Immediate Past President]

Thats a bummer 
But this is where you see the benefit of running a cheap automotive engine, 1 day in the shed and you will be back on the river.
If your South Island wreckers are too much of a rip off I have a j30 you can have? Freight will cost a bit tho.
I agree with Jeff, detonation likely cause......
Do you have an oil cooler? 90?c is pretty cool unless you were just cruising along.