Topic: Need help with my970cc project

[awiertalla]

Alright, I've spent the better part of a year building a 1978F into a 970cc monster, and now I need help with the carb jetting (or what I assume is carb jetting). I will list the parts I have in the motor for reference, but when I try and kick it on, I get a fire or two, at very most 4, and it's off again. A couple backfires out the carb as well. I'm running 42mm mikuni 2 into 4 with velocity stacks and open 4 into 4 pipes. Any help you guys can provide is much appreciated!Oh, I also tightened my spark plug gap.

Engine:
Mikuni 42mm 2 into 4 (velocity stacks)
kenny D grind cam
R.C engineering head (opened to 970)
weisco pistons
970 block from cyclex
4 into 4 open pipes
cyclex optical timing
lightened and balanced crank
heavy duty crank arms
heavy duty engine studs
cyclex racing transmission
racing clutch
cyclex exposed stator (kick only bike)
Motogadget M-unit power commander
All new chains, bearings and seals

Pics are a little outdated, I'm running a remote oil filter located behind the engine, as well as a much larger oil cooler than is what is in the photo. Gotta make sure it stays cool!

[turboguzzi]

welcome. sounds like a nice build. with pics it would be even nicer
could be ignition timing off, try to advance it more

hope you also dont have cyls 1-4 and 2-3 wires crossed up... check it too by simply swapping wires to the plugs.

[awiertalla]

It has high output coils provided with the cyclex optical ignition, and the coils are labeled for what cylinder they are supposed to go to. But I had indeed wired them incorrectly a couple weeks ago, but caught it before I started trying to turn the bike over. Appreciate the help! I'm willing to double check and try anything

[scottly]

I agree that the ignition timing is the first suspect; the power-arc system deletes the stock timing marks when installed, making it difficult to verify.

[MRieck]

So what do use? A cam timing wheel? I have never used one of those systems.

[scottly]

Proponents of the system recommend a soda straw inserted into the spark-plug hole to "determine" TDC.

[Old Scrambler]

Assuming you timed it to #1 and have the cam dialed-in................those HUGE carbs won't flow unless you have significant rpms. How much choke are you using? Maybe you could get rolling down a long hill and start the motor in 2nd gear or higher. Your idle speed may not be lower than 2000 rpms

[Retro Rocket]

Assuming you timed it to #1 and have the cam dialed-in................those HUGE carbs won't flow unless you have significant rpms.

From what I gathered the OP  has one of those cyclex 4 into 2 carb set ups, so he is only using 2 carbs. If you want to get the most performance out of that engine, get rid of those carbs and go back to a bank of 4 CR29's or RS34's....

[dragracer]

I've never used that ignition system myself but it does seem like an ignition timing issue. I'd use a piston stop to find true TDC once I got a degree wheel and pointer set up.  You could then be sure where to set the static timing. We have problems with the marks on the dyna pro series rotors often being anywhere from 3-6 degrees off and have to scribe new mark for our baseline timing. You can't just check 1-4 either, you have to check 2-3 as well.

As to the carbs,on a kick start only high compression engine, I've found that a quick squirt of fuel from a spray bottle works wonders on the first start up. Wouldn't recommend ether😓.

[calj737]

So what do use? A cam timing wheel? I have never used one of those systems.

Once the cam is properly degree'ed in, you install the ignition plate and rotate the plate until it lights up (powered on a switched 12v circuit), signaling #1 F mark. There are reference marks on the base plate as well. Its a nice system if you subscribe to the multi-spark theory and their multiple curves embedded for tuning.

[PeWe]

Why not a first test with OEM ignition, points? Easy to setup. When it runs well check carbs and install the new ignition and concentrate on that.

[madmtnmotors]

Why not a first test with OEM ignition, points? Easy to setup. When it runs well check carbs and install the new ignition and concentrate on that.

That's how I do every build. Set up initially with points to help eliminate as many "variables" as possible. I'll often run the points ignition for the first 500 mile break in before switching out the ignition.

[awiertalla]

So what do use? A cam timing wheel? I have never used one of those systems.

I used a camshaft degree kit to find tdc and dial in the cam shaft with the cam chain, cam sprocket, crank sprocket. Takes a little to wrap your mind around it, but was really helpful

[awiertalla]

I've never used that ignition system myself but it does seem like an ignition timing issue. I'd use a piston stop to find true TDC once I got a degree wheel and pointer set up.  You could then be sure where to set the static timing. We have problems with the marks on the dyna pro series rotors often being anywhere from 3-6 degrees off and have to scribe new mark for our baseline timing. You can't just check 1-4 either, you have to check 2-3 as well.

As to the carbs,on a kick start only high compression engine, I've found that a quick squirt of fuel from a spray bottle works wonders on the first start up. Wouldn't recommend ether😓.

I actually did use a degree wheel and piston stop to find tdc on #1 for my static timing. But I only checked #1, does it realy changed between the other 3?

As for the kickstart on a high compression motor..... yah I messed that up hahaha. I loved the exposed alternator, and I have a 71 sohc kick only, and there is something about it that is just awesome. I have to stand on the bike to get enough to kick it on (I realize I run the risk of bending my kickstart shaft)

[awiertalla]

This is helpful, I will have to pick up a pair of points. The existing bike was in very poor shape and I don't want to rely on those. My other sohc has a dyna system in it.

[scottly]

I've never used that ignition system myself but it does seem like an ignition timing issue. I'd use a piston stop to find true TDC once I got a degree wheel and pointer set up.  You could then be sure where to set the static timing. We have problems with the marks on the dyna pro series rotors often being anywhere from 3-6 degrees off and have to scribe new mark for our baseline timing. You can't just check 1-4 either, you have to check 2-3 as well.

As to the carbs,on a kick start only high compression engine, I've found that a quick squirt of fuel from a spray bottle works wonders on the first start up. Wouldn't recommend ether😓.

I actually did use a degree wheel and piston stop to find tdc on #1 for my static timing. But I only checked #1, does it realy changed between the other 3?

No, there is no separate adjustment for 1-4 and 2-3 with the power arc.
BTW, are you using a battery with the exposed charging system?

[754]

+1 on priming with raw gas injected sparingly..... If it then tries to run..you got carb problems..

[madmtnmotors]

My other sohc has a dyna system in it.

Maybe borrow the Dyna S? It's a known good working ignition?

[scottly]

My other sohc has a dyna system in it.

Maybe borrow the Dyna S? It's a known good working ignition?

1+

[PeWe]

Points have separate adjustment for 1-4 & 2-3.
I'll check TDC on 4 and 3 and check the T  markings for accurate setting in my current build that will have min CR 10.5:1 maybe more. I have seen that 2-3 runs hotter several times. Once fatal.

- CB9000 DOHC 0.8kW starter motor might be needed to crank a 970cc?
Edit: I see now that you will not use electrical starter.

- Is it the CR12.5:1 970cc kit that CycleX sells?

[754]

Were your carbs jetted in thr ballpark range?
Where is that guy ?

[Bill/BentON Racing]

G'luck,  not a matter of if you'll bend the kickstarter arm and shaft, its a matter of when lol! I've bent a new one first weekend out!

[754]

I hope you add rear motor mounts..

[scottly]

Just saw the pics added to the first post. The starter cavity is the worst possible place to mount a battery.

[calj737]

Just saw the pics added to the first post. The starter cavity is the worst possible place to mount a battery.

And the Reg/Rec and M-Unit mounted to the case leaves some questions too