Author Topic: Need help with a 970 big bore project  (Read 1622 times)

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Offline awiertalla

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Need help with a 970 big bore project
« on: July 25, 2018, 11:25:37 am »
Alright guys, I have been building what was a 1978 CB750F for the past 3 years. I pumped it up to 970cc, and now that it is complete and ready to start, I am getting nothing when I kick it over. I will list what I feel are critical parts to help everyone understand what I have going on. I have also called Ken from CycleX, who is a great resource, but he is frustrated at the lack of info I can give him. I really appreciate his time and want to make it worth the phone conversation, so here I am.

Donor Bike 1978 CB750F (blown up because of the valve issue the F’s had)

Cycle X Mikuni 34mm 2-4 carbs with velocity stacks (jetted from Cycle x, Ken said it should be good enough to at least start the bike with what they install)
970cc weisco pistons
Cycle x balanced/lightened crank
Cycle x heavy duty connecting rods
Heavy duty engine studs
Heavy duty cam chain
Cycle X optical ignition (I ran switches, to adjust the timing curves at the bars)
Coils, plugs and wires were purchased with the cycle X igntion (they are made for eachother)
Motor gadget M-unit for a power commander
Shorai battery
Adjustable cam tensioner
R.C. Eng head
       (This was just completely redone by A.P.E, stainless oversized valves, bronze guides, titanium keepers, ported and polished intake and exhaust, blended 970cc combustion chamber)
Kenny D hot cam
Adjustable cam sprocket (came with the R.C head, has 3 holes, one stamped 5, another 8, and one has nothing)
Remote oil filter, with a oil cooler set up on front of bike
Cycle X exposed alternator, with provided reg/rectifier (running kick only because you have to remove the starter motor for this alternator)

So my thought is the lack of anything is related to my cam and oversized valves, but I was hoping for some direction on how to time and intall this. I installed the cam as you would normally would, parallel line with the cam tower, notch upwards, cycle x ignition TDC for 1 and 4(you remove the stock advance weights and timing marks unfortunately). I used the unmarked holes on the adjustable cam sprocket, and I am running a lightly aggressive timing curve suggested by Ken.

I have strong spark on all 4, I have (new and cleaned) carbs, and the timing is static timed. When I kick it over though, I get nothing. The most I have gotten were some pops out the carbs, and I tried using some carb cleaner to rule out fuel delivery and the carb cleaner caught on fire in one of the velocity stacks, but it didn’t make any significant noise.


My questions really are, what is the proper was to install the Kenny D hot cam, and what do the 5 and 8 stamped on the sprocket mean? I am thinking they signify a degree of advance or retardation, but I don’t know enough and race bikes to choose one or the other. Any and all help is much appreciated, I am willing to try any advice, and cross it off as a potential problem.

Another question I have is about running a VOES switch for this, I am not currently running a voes switch, but I am wondering if this application would require one or not.

« Last Edit: July 26, 2018, 08:07:09 am by awiertalla »

Offline kmb69

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Re: Need help with a 970 big bore project
« Reply #1 on: July 25, 2018, 12:56:12 pm »
Does "getting nothing" mean no compression?

Offline BPellerine

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Re: Need help with a 970 big bore project
« Reply #2 on: July 25, 2018, 01:06:30 pm »
the 5 and 8 are diff degrees of advance or retard for timing the cam,most use a slotted sprocket these days,if you are just trying to start it you might want to set the cam in stock position and then time the cam for perf after.
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Offline PeWe

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Re: Need help with a 970 big bore project
« Reply #3 on: July 25, 2018, 01:16:14 pm »
Most basic to get an engine to start
- Fuel to carbs-->into head?
- Ignition OK on all plugs, when it should. ?
Not swapped wires to coils so 1:4 get signal for 2:3 and opposite
« Last Edit: July 25, 2018, 01:18:32 pm by PeWe »
CB750 K6-76 1005cc JMR Billet block.
CB750 K2-75 stock looking project started 2017

Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #4 on: July 25, 2018, 01:19:27 pm »
the 5 and 8 are diff degrees of advance or retard for timing the cam,most use a slotted sprocket these days,if you are just trying to start it you might want to set the cam in stock position and then time the cam for perf after.


Cam is currently set to stock, using the unmarked hole on the cam gear (I assumed was stock)

Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #5 on: July 25, 2018, 01:20:24 pm »
It has compression, sleeves and pistons provided by Cyclex

Does "getting nothing" mean no compression?

Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #6 on: July 25, 2018, 01:24:37 pm »
I ran a vented auxiliary gas bottle to try and start it, so yes for gas to carbs. Also tried to open the throttle and squirt carb cleaner in, in order to cross off fuel delivery as an issue.

I have checked 1-4 and 2-3 wires, but I can triple and quadruple check. Let’s assume they are correct.

And there is ignition to all wires, strong spark on them all. Timing based on stock install and timing.

Most basic to get an engine to start
- Fuel to carbs-->into head?
- Ignition OK on all plugs, when it should. ?
Not swapped wires to coils so 1:4 get signal for 2:3 and opposite

Offline underdog

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Re: Need help with a 970 big bore project
« Reply #7 on: July 25, 2018, 01:43:38 pm »
  Probably not the cam unless you are way off and then you would probably valve to piston issues. Mine did the same thing initially because I had misread those tiny #'s stamped in the coil. Once I had them in the correct order it fired right up.  :)

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Need help with a 970 big bore project
« Reply #8 on: July 25, 2018, 01:44:59 pm »
First, I would question this - (I ran switches, to adjust the timing curves at the bars)

Second, you should degree the cam.
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Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #9 on: July 25, 2018, 02:08:24 pm »
  Probably not the cam unless you are way off and then you would probably valve to piston issues. Mine did the same thing initially because I had misread those tiny #'s stamped in the coil. Once I had them in the correct order it fired right up.  :)

I will happily check this when I get home tonight, lets hope I am a ditz and swapped them somehow!

Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #10 on: July 25, 2018, 02:15:52 pm »
First, I would question this - (I ran switches, to adjust the timing curves at the bars)

Second, you should degree the cam.


I also thought it could possibly be the switches, but they operate off of grounding 2 different wires in a combination. Worst case scenario, is they are both grounded and I am running a moderately aggressive timing curve.

I degreed the cam when I installed it originally, I have since had the head redone, do I nee to degree it again?


Offline slikwilli420

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Re: Need help with a 970 big bore project
« Reply #11 on: July 25, 2018, 06:31:31 pm »
What is the dial indicator checking in the picture? There isn't any reason I'm aware of to have it set up like that. You need to be checking lift numbers from the spring retainer making sure the dial shaft is parallel with the valve stem.
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Offline BPellerine

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Re: Need help with a 970 big bore project
« Reply #12 on: July 25, 2018, 06:38:11 pm »
and how do you degree it with fixed holes for advance/retard in the sprocket?
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Offline calj737

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Re: Need help with a 970 big bore project
« Reply #13 on: July 26, 2018, 03:34:37 am »
I would revisit the install of the optical ignition. It is far more likely you have that installed 180* out and are firing in reverse. You have spark (you claim) but very likely at the wrong time on the wrong cylinder.

Reset the motor to true TDC for cylinder 1 and mark the case behind the ignition plate. Then work on timing the ignition from there.
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Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #14 on: July 26, 2018, 07:12:34 am »
What is the dial indicator checking in the picture? There isn't any reason I'm aware of to have it set up like that. You need to be checking lift numbers from the spring retainer making sure the dial shaft is parallel with the valve stem.

I was degreeing the crankshaft to the cam shaft. I used a piston stop, and marked my stop on the white wheel on the end of the crank, reversed it, diveded the difference to find my exact tdc. The dial on top was giving me the exact lift of my cams in relation to where my pistons were currently at in reference to tdc
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Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #15 on: July 26, 2018, 07:19:17 am »
I would revisit the install of the optical ignition. It is far more likely you have that installed 180* out and are firing in reverse. You have spark (you claim) but very likely at the wrong time on the wrong cylinder.

Reset the motor to true TDC for cylinder 1 and mark the case behind the ignition plate. Then work on timing the ignition from there.

I’m not sure why you put the claim in there, but yes I have spark. I have checked it in multiple ways, pullling each plug, putting it to ground and watching it spark. I checked the ohms on my coils, which checked out fine. I also used a timing light to checked power is going to coils at proper times, which it does, proper is a relative statement.

I will triple check the install of the ignition, but I installed it according to a stock install. Raising #1 to tdc using a screwdriver in spark plug hole, role it to the top, slightly past then go back a hair. TDC and the cam are set to the on the dot.


Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #16 on: July 26, 2018, 07:22:23 am »
and how do you degree it with fixed holes for advance/retard in the sprocket?

The first time i degreed it, I had the stock cam gear installed, not the R.C one. I am also currently not using the advanced or retarded holes in the sprocket I have, that was one of the questions I was asking, should I be using one of them for the cam I have installed?

Offline slikwilli420

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Re: Need help with a 970 big bore project
« Reply #17 on: July 26, 2018, 08:00:59 am »
What is the dial indicator checking in the picture? There isn't any reason I'm aware of to have it set up like that. You need to be checking lift numbers from the spring retainer making sure the dial shaft is parallel with the valve stem.

I was degreeing the crankshaft to the cam shaft. I used a piston stop, and marked my stop on the white wheel on the end of the crank, reversed it, diveded the difference to find my exact tdc. The dial on top was giving me the exact lift of my cams in relation to where my pistons were currently at in reference to tdc
,

Pretty sure this isnt a thing. Find TDC using a piston stop, and while piston #1 is at TDC, install cam with line horizontal and notch up (I believe) and then you can start to degree the cam.

and how do you degree it with fixed holes for advance/retard in the sprocket?

The first time i degreed it, I had the stock cam gear installed, not the R.C one. I am also currently not using the advanced or retarded holes in the sprocket I have, that was one of the questions I was asking, should I be using one of them for the cam I have installed?

If you have a stock gear, there is nothing to degree. You need to swap in the one with different hole positions or better yet, a slotted cam gear so you can get it right on the money compared to cam card. You will need to get the right cam gear and install it on the cam, and start over with degreeing the cam, starting with TDC location. Once you have it set once, you could scribe around the bolts head so when you reinstall the cam gear later, you can get damn close to your original specs.
All you gotta do is do what you gotta do.

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Offline underdog

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Re: Need help with a 970 big bore project
« Reply #18 on: July 26, 2018, 08:17:29 am »
   Even if your cam was off a little, it would start. Having the cam degreed to where you want it is important, but I'm pretty sure that isn't the starting issue.  Double check the ignition timing, it sounds like that's your trouble. Really its only 2 possible things,  the optical wheel isn't on TDC when it should be or plug wires mixed up. Don't worry about the advance curve wires either, that won't be it. I do wish I had that advance curve knob though! :)

Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #19 on: July 26, 2018, 10:40:37 am »
This is excellent information! I will purchase a slotted cam gear today. As for the cam card, I do not have one, but will spend some time and find the specs on-line. I purchased the head, jugs, and cam off ebay a couple years ago, it did not come with the card. Thank you so much for providing clear instructions on this. When I degreed the cam in the photo, I was following the instructions that came with my cam degree kit. I know how to build a stock 750, but this is much more than that, so I have to spend the time and learn this new stuff. I sincerely appreciate the people who take the time to provide quality info like this, I am trying to approach this with my ego set aside, and the thought that I know nothing haha.

What is the dial indicator checking in the picture? There isn't any reason I'm aware of to have it set up like that. You need to be checking lift numbers from the spring retainer making sure the dial shaft is parallel with the valve stem.

I was degreeing the crankshaft to the cam shaft. I used a piston stop, and marked my stop on the white wheel on the end of the crank, reversed it, diveded the difference to find my exact tdc. The dial on top was giving me the exact lift of my cams in relation to where my pistons were currently at in reference to tdc
,

Pretty sure this isnt a thing. Find TDC using a piston stop, and while piston #1 is at TDC, install cam with line horizontal and notch up (I believe) and then you can start to degree the cam.

and how do you degree it with fixed holes for advance/retard in the sprocket?

The first time i degreed it, I had the stock cam gear installed, not the R.C one. I am also currently not using the advanced or retarded holes in the sprocket I have, that was one of the questions I was asking, should I be using one of them for the cam I have installed?

If you have a stock gear, there is nothing to degree. You need to swap in the one with different hole positions or better yet, a slotted cam gear so you can get it right on the money compared to cam card. You will need to get the right cam gear and install it on the cam, and start over with degreeing the cam, starting with TDC location. Once you have it set once, you could scribe around the bolts head so when you reinstall the cam gear later, you can get damn close to your original specs.

Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #20 on: July 26, 2018, 10:45:41 am »
I really appreciate all the info, I like what you and a previous poster said: Install a slotted cam gear, degree the cam with the card, in the meantime I will quadruple check ignition timing and plug orientation before attempting to start it up again.

As for the curves, I just used two silver toggle switches, they flip independently for the brown or blue wire. It’s dumbed down, but should serve the purpose I need. 

   Even if your cam was off a little, it would start. Having the cam degreed to where you want it is important, but I'm pretty sure that isn't the starting issue.  Double check the ignition timing, it sounds like that's your trouble. Really its only 2 possible things,  the optical wheel isn't on TDC when it should be or plug wires mixed up. Don't worry about the advance curve wires either, that won't be it. I do wish I had that advance curve knob though! :)

Offline slikwilli420

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Re: Need help with a 970 big bore project
« Reply #21 on: July 26, 2018, 11:46:31 am »
Good luck to you. Get that cam and ignition dialed in and that thing should pull your arms out of their sockets.
All you gotta do is do what you gotta do.

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Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #22 on: July 26, 2018, 01:12:44 pm »
Good luck to you. Get that cam and ignition dialed in and that thing should pull your arms out of their sockets.

Thank you! And thanks for the input, Ive ordered the slotted cam gear from APE, should have it by next week. Ill search around for a cam card, and see where I can go from there. It’s going to be a bar/show/event bike. No padding on the seat, and fairly uncomfortable position, but I have other bikes that fill those needs. This bike was intended to push my knowledge and understanding of motors and how to build them, so far it’s doing its job well.

Offline slikwilli420

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Re: Need help with a 970 big bore project
« Reply #23 on: July 26, 2018, 01:18:22 pm »
Someone should have specs for the KHD cam. Matter of fact, check here:

http://www.cyclexchange.net/camshaftpage.htm

They have a KHD CX1 cam that should get you damn close.
All you gotta do is do what you gotta do.

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Offline awiertalla

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Re: Need help with a 970 big bore project
« Reply #24 on: July 31, 2018, 12:29:32 pm »
I recieved the slotted cam sprocket the other day. I disassembled the top end again in order to put a dial indicator directly on the piston to get the most accurate tdc, so I can mark the case this time (should have done this the first time). What I found though upon disassembly, was the valves on #1,4 were kissing the pistons. I am unsure how to proceed with this, could it just be the cam needs adjustment or do I need to get a thicker head gasket and possibly shave the pistons down? This all makes sense to why the bike wouldn’t turn over.

 

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