Author Topic: cb750 doesnt start (Read 2491 times)

puffpd · « **on:** January 24, 2006, 04:43:05 PM »

hi,

i have a 1975 cb750 super sport. It was starting fine. yesterday while kick starting the bike i heard a couple of loud back fires and then left it alone.

Today when i tried to start the bike it doesnt seem to start.
What may be the problem? and how do i go about fixing it?

Thanks

brewbrother · « **Reply #1 on:** January 24, 2006, 05:03:50 PM »

I'm not the most mechanically inclined person, but start with the most basic and work your way up. Its the bike getting fuel?? Is the bike getting spark?? Is the bike getting air to the carbs?? No doubt more experienced posters will step in when you provide more info including what kind of up keep you do and whether the bike is getting fuel, spark and air. I experienced a performance problem with my CB and it was all related to maintenance that I was not doing. Best of luck.

ProTeal55 · « **Reply #2 on:** January 24, 2006, 05:06:35 PM »

It has to be one of three things...

1. FUEL
2. AIR
3. SPARK

As BrewBrother said, check the obvious things, such as the battery, carbs, fuel , etc...
After that, You might have to do alittle more "digging around" to find your issue...

Could be something as simple as the fuel petcock was in the off position, and the carbs. eventually
ran out of fuel....?

KCs76Cafe · « **Reply #3 on:** January 24, 2006, 07:04:00 PM »

All it took for my $220 76 750K that had set for close to a year to start was a new set of spark plugs.

The PO was wanting $450 for it....he got frustrated with it not starting. Offered him $200 and he took it....plus $20 to deliver it.

Since yours was running recently.....its got to be something simple.

puffpd · « **Reply #4 on:** January 24, 2006, 07:30:19 PM »

it was in the rain for a day but it started after that, do you think the water migh have caused some damage???

TwoTired · « **Reply #5 on:** January 24, 2006, 11:00:54 PM »

Check for water under the points cover and on the points. The common cork gasket there is not reuseable. I made one from hardware store neoprene that seals much beter and is reuseable. But, just to get you going again, keep the points dry.

One possibility, anyway.

cadler · « **Reply #6 on:** January 25, 2006, 02:12:37 AM »

make sure your kill switch is on and working correctly.

puffpd · « **Reply #7 on:** February 06, 2006, 07:06:32 AM »

it finally started,

I had to change the spark plugs and charge the battery. However the second day, i had trouble starting it. It would start and then go dead again. Any ideas why this may be happeneing. I am assuming the carbs need cleaning. Well i am new to this. The only thing i can think of doing is , pulling out the carbs and getting it cleaned from some one who does carbs.

Any idea how much it would cost me?

Thanks

Gordon · « **Reply #8 on:** February 06, 2006, 07:12:26 AM »

Quote from: puffpd on February 06, 2006, 07:06:32 AM

Any idea how much it would cost me?

Thanks

More than it's worth. And there's still no guarantee that it will be done right.

Lumbee · « **Reply #9 on:** February 06, 2006, 02:23:01 PM »

..carbs are a right of passage on these bikes...your only gaurantee for clean carbs is to do it yourself...

Bob Wessner · « **Reply #10 on:** February 06, 2006, 02:27:55 PM »

Quote

..carbs are a right of passage on these bikes...your only gaurantee for clean carbs is to do it yourself...

Doing them more than once is not unheard of. Ask me how I know.

TwoTired · « **Reply #11 on:** February 06, 2006, 02:55:37 PM »

Quote from: Bob Wessner on February 06, 2006, 02:27:55 PM

Doing them more than once is not unheard of. Ask me how I know.

okay Bob...how do you know?

I can usually do the manual slide carbs on the 1st try...now now that I've done quite a few.

I've done the CX's CV carbs 4 times now, with a fifth yet to go. But, I've since learned there is a hole in my fuel filter.

If I found that first, I wonder... At least there is only two.

Where are you located, puffpd?

puffpd · « **Reply #12 on:** February 06, 2006, 03:53:20 PM »

hi ,

i am in norfolk, virginia. thats gonna be a tough one, cleaning the carbs. i dont know if i will be able to put it all together.

puffpd · « **Reply #13 on:** February 06, 2006, 03:54:17 PM »

also, there is a burning smell when i turn the engine on. how can i be sure if the oil is flowing through. i checked the oil level, it seems fine.

Lumbee · « **Reply #14 on:** February 06, 2006, 06:56:30 PM »

...you can pull the oil cap and look for the oil swirling around while its running...

...u can clean the carbs...just take u'r time...get a bunch of zip lock bags so you keep track of everything...its easy to die a thousand deaths fearing one...

6adan · « **Reply #15 on:** February 06, 2006, 07:25:09 PM »

If it starts after charging battery and then will not next day you may have a bad battery or something shorting it out or engine not charging.Dannie

Kevin D · « **Reply #16 on:** February 06, 2006, 07:34:34 PM »

puffpd, Introduce yourself to your carbs: drop the float bowl off of one and have a look for crud in the bottom. Does your SS have a

hinged wire holding the bowl on the bottom like my K1? If so, push both sides of the wire forward and the bowl should drop right

off or come loose with a very gentle tap. If the bowls are spotless and mostly filled with gas then the carbs might be OK.

Keep that battery charged and the bike dry. For myself, I've had (a very little) trouble with bad spark plug caps. But I'm not nearly as

expert as many of the guys here. Nose around a little bit and you will find carb photos.

puffpd · « **Reply #17 on:** February 08, 2006, 11:56:39 AM »

another question,

the bike starts well with the choke on and when the enfine is cold. Once iput the choke off, the bike dies, also after running it for 5 minutes it dies.

i am only worried about the oil not flowing. Any idea what may be going on with the bike?

Lumbee · « **Reply #18 on:** February 08, 2006, 12:02:29 PM »

...if it starts only with the choke on thats usually an indication the idle jets are clogged...

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Author Topic: cb750 doesnt start (Read 2491 times)

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