[72cb350]

hello and thank you for taking the time to read, and hopefully, respond to this thread.

I bought my first motorcycle last summer. it is a 72 Honda cb350. I rode it around town for a while and when I got an internship I rode it approximately 70 miles to and from the workplace. Unfortunately, the second time I made the trip, i blew a head gasket and warped the head. I took the easier route and bought a running engine. It sat around for awhile until a few weeks ago when I finally got around to working on it. I pulled out the busted engine and put in the new one. It turns freely, everything is in its place, but it won't start. The only sign I have of something being wrong is that the neutral light does not turn on even though the headlight, taillight, brakelight and turn signals work. I also recently put in a new battery.

When I use the kick starter, at most I get a few turns of the engine out of it...meaning it goes puh puh puh puh puh....then dies....ha.

Anyways, I am not at all a mechanic. I did the entire engine swap by using a clymer manual. I feel as though I am so close to getting her running that I can taste it. All I want to do is ride again!!!!

Any info or words of advice would be greatly appreciated

 

[WintrSol]

Did you actually observe the replacement engine run?

Did the replacement engine include mounted carburetors, or did you have to disturb them?

Are you using the choke, and do you ease it off as soon as there are signs of life?

Treat the gas with a good fuel system cleaner, like Seafoam, mix it by rocking the bike, then put a catch can under each carburetor and open the drain until about a cup dribbles out, then close the drain. Let sit for a few hours or overnight, then try starting.

The neutral light is a common issue on Hondas of that vintage; the one on my CB450 comes and goes, so I just feel it into neutral most of the time.

 

[72cb350]

Thank you for your response!

To be honest, I bought the engine on ebay. However, the seller did send me a video of the engine running.

The engine did not have mounted carburetors, I took them off the old bike and put them on the new engine...so they have been moved around quite a bit and they have also been sitting awhile. I took the cases off the bottoms where the floats are and sprayed them with carb cleaner and made sure they were operating properly.

I am using the choke.

Fuel system cleaner sounds like a good idea...

Could it be that the points and ignition timing need to be adjusted? It's just a hunch but I feel like when it does fire (generally only about three or four times), i only hear the ignition coming out of one exhaust pipe...?

Again, I'm new to this so any help you can offer is greatly appreciated.

Thanks again!

 

[WintrSol]

Couldn't hurt to check the points and timing. I was thinking more that the carburetor mounting boots may be leaking, as it is easy to get them in a little out of proper alignment. Also, many get small cracks which may look innocent, but leak plenty. You may want to salvage the set from the old engine, just for good luck.

It's not uncommon to get fire on only one side, if the carbs aren't tuned in. Once one side starts firing, and you get a little heat going, the other side will often pick up, so you can start tuning it in.

 

[72cb350]

Where are the carburetor mounting boots located? Are those the rubber circles on the cylinder head into which the carbs attach to the engine? If so, I pulled the carbs off of them a few times because I had to backtrack. However, I do have clamps on them...

I'm pretty confused when it comes to adjusting the points and timing. I've never done this stuff before so I'm shooting in the dark.

I can't get anything to fire now... I wish I could get one side firing so I could tune the carbs but I can't even get any sign of ignition.

I kick it and get nothing. No delicious sound of a working engine... just....bleh. I am beginning to get very frustrated...

 

[WintrSol]

The rubber 'rings' bolted to the head are the boots; the carbs have to be fitted all the way in, so that the boot is even around the front of the carb. If they aren't seated correctly, the clamp won't seal them.

The points are under a cover on the left side of the head. See this video to get started:

The points gaps are set, then the plate is adjusted so that the left points just open at the LF mark. Then, you move to the other set, and make sure they open at the other F mark. The plate often has enough movement so that shifting them can get both to open at the correct mark. If not, the gap is tweaked a bit on one set to get them both correct. While you're under that cover, look to see if the points appear burned or overly worn.

 

[keitth43]

Poorly Engine

Did you install brand new spark plugs ?

Is the Ignition Timing correct ?

keitth43

 

[Hansen58]

Sounds like a spark issue to me, just from my experiences.

 

[J-Rod10]

Try a little starting fluid, see if it fires up. I'd probably change the plugs on it as well. And, checking the points aren't the worst idea.