new guy cb750 build

[crawdadman]

So ive been working on this bike for about 9 months now. I purchased it from someone off craigslist for 500 bucks. It was completely pulled apart, and had no idea if it ran.
I got it running rough about 6 months ago, and since then have been making it my own creation! but unfortunately it is not alive :'( I even threw in some cbr600 coils, but to no per-vale..The bike turns over good, but just wont fire...sounds like fuel to me. carb 3 needs the float adjusted, but that shouldnt stop it from firing?
I also ordered some rings off ebay when i had the motor apart. I specifically remember ordering dohc rings. but someone wrote on the box sohc only!! i did some investigating and was told that that would not matter. the ring size is the same...was i ill informed?
I have so many more questions, if anyone can lend there wisdom?
Also using a lawn mower starter lol!!

 

[Rich Ard]

Lot of DOHC 750s lately! Nice work on the tank.

And that's a lawnmower solenoid - I was really hoping to see a Toro starter motor

 

[crawdadman]

also didnt like how low the frame was were the seat was. probably should have made the rear fender detachable lol.

 

[crawdadman]

ya, not so good with terms rich lol. but whatever works i guess.

 

[volthause]

I can dig it. On-board to see where this goes.

 

[crawdadman]

good compression! getting fuel! BUT STILL NO SPARK! my harness is in shambles at the moment, but pretty sure it is put together right. anyone got any ideas?

 

[surffly]

Those cheap/junk emgo pods are not going to make running/tuning an easy job.
The CV carbs HATE pods, emgo even more.

 

[notlob]

Looking good there.

You need to check out your pulse coils and regulator/rectifier if you are getting no spark. There is a proceedure for doing it in the manual, do a search online and you'll find one to download. I bought two non runners and both had a bad pulse coil. Its unlikely to be the ignitor boxes as they are quite robust and rarely fail.

The CBR600 are a good upgrade.

 

[crawdadman]

Those cheap/junk emgo pods are not going to make running/tuning an easy job.
The CV carbs HATE pods, emgo even more.

yes, I do regret those. but i am gainfully unemployed, thus some cheap parts.
But didn't slack on the internals of the carbs. got a step by step on how to make the cv carbs work good with the pods.

 

[surffly]

Better option, and in most cases would be free, is to run the stock air box.

 

[crawdadman]

Looking good there.

You need to check out your pulse coils and regulator/rectifier if you are getting no spark. There is a proceedure for doing it in the manual, do a search online and you'll find one to download. I bought two non runners and both had a bad pulse coil. Its unlikely to be the ignitor boxes as they are quite robust and rarely fail.

The CBR600 are a good upgrade.

I actually threw new cbr600 coils on it today. It has to be electrical, because i had it running before.

 

[crawdadman]

Better option, and in most cases would be free, is to run the stock air box.

well.....airbox wont fit anymore. the frame has been altered lol

 

[LBC]

Lot of DOHC 750s lately! Nice work on the tank.

And that's a lawnmower solenoid - I was really hoping to see a Toro starter motor

+1 on the tank!

and

+1 on the starter

 

[LBC]

yes, I do regret those. but i am gainfully unemployed, thus some cheap parts.
But didn't slack on the internals of the carbs. got a step by step on how to make the cv carbs work good with the pods.

My CB900 runs great with the pods and stock CV carb. Follow the free carb rebuild guides to the letter and you should be fine. Just be patient.

Electrical work takes me twice the time that anything else does. My eyesight just isn't good enough to see which ways those electrons are moving.

 

[crawdadman]

My CB900 runs great with the pods and stock CV carb. Follow the free carb rebuild guides to the letter and you should be fine. Just be patient.

Electrical work takes me twice the time that anything else does. My eyesight just isn't good enough to see which ways those electrons are moving.

Thanks LBC! I did follow the carb rebuild guide, its definitely getting fuel, and spark. I'm thinking maybe valves, or the gap on the points maybe.

 

[VonYinzer]

Did you set the timing correctly?

 

[notlob]

I really do suggest you download a manual. You need to check first your valve timing and gaps if you have had the head off. Then work though the checks on the electrical side. pulse generator gaps (you dont have points), then checks to ascertain if the pulse generators, ignitors. generator and reg/rect are ok.
If your your happy with all that move on to the fuel system.

 

[crawdadman]

I really do suggest you download a manual. You need to check first your valve timing and gaps if you have had the head off. Then work though the checks on the electrical side. pulse generator gaps (you dont have points), then checks to ascertain if the pulse generators, ignitors. generator and reg/rect are ok.
If your your happy with all that move on to the fuel system.

The bike actually came with a manual. the valves are only off by .001. it has spark, and it is getting fuel. would it still get spark if the gap in the pulse generator is off? sorry for all the wrong terms, i am young and still learning lol

 

[coyote13]

If you've got spark and fuel but no fire, might want to check compression.


or maybe think about finding a stock airbox :-X

 

[notlob]

Its best to set the pulse generator coil gap to the lower end of the range. Like coyote says I'd be checking compression as well. You might still get a spark at the plug when its outside but it could be failing under compression which would rule out the low compression, but that generally happens more often than not at higher revs.
Set the pulse generator gaps to the lower setting, check the timing is correct as per the manual, ensure you have a spark from both coils, thats plugs 1or 4 and 2 or 3. If all that is OK and still not starting its looking like a fuel issue as even with a lowish compression you should at least some firing.
One other thing you could try. The CB900 I'm doing now I tried to get it running with the plugs it came with I was getting a good spark on one plug and weakish one on the other three. this was after replacing a duff pulse coil. Thought it may just have been they weren't grounding properly when I was testing them. But it was difficult to start and wouldn't rev. Turned out to be the three plugs were faulty, ran fine with new plugs in.

Dont apologise for your age, we've all been there and were still learning now. At least you have a lot of info somewhat readily available on forum like this. We had to go creeping to the older kids with bikes to get our info.