If that CB750 is original, with factory exhaust not rusted out, it’s one of the more valuable bikes from that era. BIG market for them.
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Everything on the bike is stock, including the 4 chrome exhaust assemblies, not rusted. I believe it’s even got the original tires (They look okay, but by age I think they’d qualify for replacement.). I rode it a few times until my son was about to be born, 31-1/2 years ago. it hasn’t moved from its spot on its center stand. I gave it up to be a responsible and alive father. No one has ridden it since and I’m alive. Responsible … ?
The battery was removed in 87 and is in the garage, but I’m sure it has turned to junk by now. From time to time I think about buying a new one and firing it up, but I get over it. I can still put my hands on the title and keys.
CSA
Pour some gas in the carb. No much is needed. If it starts then you know it’s fuel. If not then spark or compression.
There are at least 2 jets and an emulsion tube and a needle/seat valve hidden in that carburetor and they all have a tendency to get gummed up. You need to find a service manual for that carburetor.
There’s one problem with that. It’s a 1987 track Olympic moped and there’s almost nothing on them in terms of manuals or diagrams, I also have no idea what kind of mikuni carb it is
I doubt you’d see any blockages and since the carb is off it would behoove you to get a spray can of carb cleaner and clean that carb.
You’ll need to screw in those screws (actually needle valves) VERY GENTLY, WHILE COUNTING EXACTLY THE NUMBER OF TURNS TO VERY GENTLY GET IT TO STOP. NEVER TIGHTEN THEM WITH ANY FORCE. Write down how many turns each screw requires to “seat.”
Then you can remove them and properly clean the holes/passages the screws seat in with the straw attached to the carb cleaner nozzle.
After cleaning it all up, including removing the float and the float needle and cleaning its seat (very possibly a non-start culprit), then you can refer to your writing to put the screws back and again TURNING THEM IN VERY GENTLY UNTIL THEY JUST COME TO REST & then turn them out the number of turns indicated for each different screw on your notes.
You should be very specific… examples: 2-1/4 turns out, 3-1/2 turns out, etcetera.
Carefully examine everything BEFORE disassembling & afterwards. Work over white cloth and pay attention to any seals, O-rings, springs, pins, etcetera, so they will go back where they belong.
Clean is the name of the game.
Get everything back where it goes and you should be fart’n through silk as that baby fires to life on just a kick or two!
CSA
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I don’t know if this is the right carb or not but all you have to do is Google mikuni carbs and there is lots of instruction and parts out there plus a few youtubes. I hope you tried spraying some starter fluid in there first to determine it is a fuel issue first though.
SORRY
Well you have received very good advice here… I dont have much in the way of answers but questions…
When did it run last? Are you using fresh fuel? Did you watch the video on how to clean all the jets in the carb? Do you have proper compression? If you have spark, then the only things you can be missing are fuel and compression. You must use fresh gasoline…drain out all of the previous fuel.
The first motorcycle I ever owned is in my shed… An Emerald Green 73’ Honda CB750, I paid $200 for it back in 88’ and while she didn’t run when I bought her, she ran shortly after a thorough carb cleaning. I really loved that bike and rode it all over this country of ours both East and West Coasts. She never let me down. I need to pull her out and get her running again. So I will be doing exactly what you are doing here, just 4x more than you. But she’ll run again, no problem.
If you have fresh fuel, spark and compression, your two stroke will run. You need to diligently check for each item as none of them are optional.
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I give you $300.
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Not to change the subject but we are talking about engines that don’t run. Before I bought my MoPed, I bought a Whizzer motor bike from a guy down the street. He warned me it didn’t run but I was about 14 and paid him $10 for it. Never could get it running. Had spark, fuel, compression, checked timing, etc. Even my BIL couldn’t figure it out. Never did get it running and don’t remember what happened to it. I guess my dad must have hauled it to the dump. Still wonder why.
Of course a few years before that I bought a pretty new B&S engine for $5. Wouldn’t run. The neighbor kid’s dad took a look at it and discovered the timing was off by a tooth or two. Ran great after that.
At any rate, if it’s mechanical, there has to be a logical reason, but doesn’t necessarily mean you ever find out what it is.
@common_sense_answer gave you great tips. My only other thought is when I work on carbs I always work over a light colored old towel. Towels are soft and things don’t bounce and roll when they fall, which they ALWAYS do at some moment.
If the timing was off on a B&S it was likely due to the woodruff key being broken.
No, the two dots weren’t aligned, which meant that someone had opened it up and maybe done some work and put it back together not matching the marks again. Then sold it as not running. I just saw it at the bike and fixit store with a $5 price on it and bought since it was near new compared to the old B&S I had.
That sounds like sabotage @bing. Or maybe some peculiar experimenting. It’s a heck of a job getting that case opened then reassembled properly for an inexperienced DIYer.
Which sounds like might have happened. A DIYer does a big job, buttons it all up, and discovers it still won’t run, and says the hell with it and dumps it. And @bing buys it. I’ve bought a Honda CL175 with exactly the same problem, and a CB360 where the breaker points cam was installed 180 degrees off and also wouldn’t run.