90 Zx750 project - ZX Forums
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post #1 of 45 (permalink) Old 06-24-2013, 04:44 PM Thread Starter
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90 Zx750 project

My gf's friend got this bike for 500 bucks. She says they drove it over but it back-fired some. I went over there to check it out and it would start for 2 seconds and turn off. Then not start again until I left it sit for an hour..then same thing, ran for 2 seconds and turns off. Not a strong run either, like it couldnt breath almost. I got the bike back to my garage.

Removed rear fairings and tail section, removed gas tank so that its just sitting on the bike, still connected.
I am pretty familiar with bikes but I'm def not a mechanic. I think I located the carbs but they dont look that dirty to me. I was wondering if anyone could send me a pic so I can have something to go on, also what should I try first to get this baby to fire up again? Thanks and I will be posting pics as I do the paint and rebuild!
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post #2 of 45 (permalink) Old 06-24-2013, 05:23 PM
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What does the inside of the gas tank look like? Is it rusted? How old is the gas that's in it? The only real way to inspect the carbs is to take the tank off then remove the carbs from the bike. Check to see if the jets are clogged and all that jazz. I don't have any pics but there are tons on the net of the zx7 carbs that can get you going until you need detailed pics or someone sends you some. Also, at that price point, I'd be prepared to change out the plugs and wires, brake pads, chain, sprockets, fuel filter, air filter and any other serviceable parts that may need to be cleaned or replaced. I hope this helps you some and get's you started.
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post #3 of 45 (permalink) Old 06-24-2013, 05:31 PM Thread Starter
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The inside of the tank didnt look bad. I dont know how old the gas is but they drove it to her house a few weeks ago Im assuming its not too old?
Is the pic I found. I can tell by the 4 black covers on top that its the same part im looking at, but I can't figure out how to get the black plastic box off the carbs to look inside. Any tips there? ALso the holes facing the camera in the pic, is this where I would squirt the starter fluid? Thank you for your quick reply =)
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post #4 of 45 (permalink) Old 06-24-2013, 08:05 PM
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You're familiar with bikes yet don't know where to spray starting fluid? Uh ok.

It goes in the BIG hole in the middle of the carb.

post a pic of the rest of the bike

Read me; you'll probably regret it.
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1994 Honda CBR900RR
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post #5 of 45 (permalink) Old 06-24-2013, 08:51 PM
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I don't know the 89-90 models as well, but from that angle of the pic, it looks a lot like a 91-92 (I am pretty sure I am right on it being at least a 91).

If it starts for a second or two, I am not sure why you need starting fluid. You have proven it is a fuel issue (not electrical). It could be dirty carbs, a rusted tank, vacuum leak or a plugged filter.

A filter is cheap. Open the fuel cap and look inside to see if it is a rusted mess. Check that all the vacuum lines are connected and not cracked. If it is none of those it needs the carbs taken apart and cleaned (and look to see that the carb tops are sealing).

As Garrett mentioned, if you do not know where the difference between the carb throat and the vent tube, you are probably best to either get some help with the carbs or take it to someone that can do it for you. We have all been there. Better to ask for help than screw things up in ignorance. These carbs are simple if you are mechanically inclined and learn the basics.

Not being an ass, just trying to not have you get in too deep and really have a problem that will cost a lot to fix.
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post #6 of 45 (permalink) Old 06-24-2013, 08:59 PM
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The way I understand his post, 57x, is that he found just a generic pic of ZX carbs and is using it as an example for his question.


I may be totally wrong; I just finished half a bottle of Doc Mcgillicuddy's.

Read me; you'll probably regret it.
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1998 Suzuki GSX-R750 x2
1993 Honda CBR900RR
1994 Honda CBR900RR
1985 Honda VF1000R
I think that's all of them?
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post #7 of 45 (permalink) Old 06-25-2013, 08:59 AM
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Doh You are correct. He did mention that he found a pic. I was not juiced and did not catch that.

The rest still stands.
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post #8 of 45 (permalink) Old 06-26-2013, 12:48 PM Thread Starter
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Wow I thought this was a place for help, not ridicule... I completely tore down my old 95 ninja and rebuilt it from the ground up so yes I'm familiar with them..but as I said I'm not a mechanic and doesn't mean I've had to spray starter fluid in a 90 zx750 before.. my bikes have never needed it..sorry I don't have your level of expertise. If I did, I probably wouldn't be here asking for help hm?



Here is a pic of where I'm at right now, I don't want to force that black box off and break something, but for the life of me I cant see whats holding it in place. I took the tank off and when I put my thumb over the hose that leads to the petcock and try to start the bike for just a couple turns, I don't feel a whole lot of suction from the tube. Any tips on getting this box off so I can look inside?

Last edited by jlkohel911; 06-26-2013 at 01:02 PM.
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post #9 of 45 (permalink) Old 06-26-2013, 01:10 PM
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EVERY god damn carb is the idea and you would spray it in the same locatio. No need to be a dickhead when I point out the fact YOU claimed to know about motorcycles yet can't find where to spray starting fluid.


Another H model is gonna die at the hands of another idiot.

Read me; you'll probably regret it.
http://oneguytwowheels.blogspot.com/

1989 Kawasaki ZX7-H1
1998 Suzuki GSX-R750 x2
1993 Honda CBR900RR
1994 Honda CBR900RR
1985 Honda VF1000R
I think that's all of them?
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post #10 of 45 (permalink) Old 06-26-2013, 01:17 PM Thread Starter
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while looking for a way to remove the black box, I noticed the airfilter pictured here.


As you can see in the following pic, its disgusting. I'm sure I'll have to get a new one of these. When I pulled the filter out I heard 'plunk plunk'. Looked inside the hole where the filter came out and saw 2 screws sitting in there? managed to get them out..
The foam on the outside of this filter is soaked with what is either oil, or gas mixed with some grease to create an oil like texture.. there is a ton of grease on the filter itself. I'm going to try to clean it up some and replace it before I work on getting another one. Could this residue be whats causing the lack of suction from the fuel hose coming off the petcock?
Thanks for the help guys I appreciate it.

Last edited by jlkohel911; 06-26-2013 at 01:20 PM.
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post #11 of 45 (permalink) Old 06-26-2013, 01:21 PM Thread Starter
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Quote:
Originally Posted by Garrett View Post
EVERY god damn carb is the idea and you would spray it in the same locatio. No need to be a dickhead when I point out the fact YOU claimed to know about motorcycles yet can't find where to spray starting fluid.


Another H model is gonna die at the hands of another idiot.
Easy killer, I said I'm familiar. Do you know what this word means? This is only my 2nd build and I've never had to spray starter fluid. I wasn't being a dick, you're the one with the attitude. There is no reason for name calling. Please be constructive in this thread, and I apologize if I have offended you in anyway. It was not my intention.

Last edited by jlkohel911; 06-26-2013 at 01:39 PM.
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post #12 of 45 (permalink) Old 06-26-2013, 02:00 PM
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Easy boys. The filter is foam and sprayed with oil, like any other ZX filter. You need to get the airbox off, it's held on by some c clamps, you may need to access them through the plug on the top of the airbox dunno, maybe Christi or Mike will chime in, I've never mess with an H, J or K for that matter. Find a service manual, it will tell you how to get it off

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post #13 of 45 (permalink) Old 06-26-2013, 02:11 PM Thread Starter
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Thank you, Azx. I managed to undo the hose to the fuel filter and unhooked the knob that changes the idle. I turned the carbs upsdie down to find them in what I believe to be pretty good shape.





I'm still kind of concerned about the lack of suction from the fuel hose tho.I'm going to replace the fuel filter and put it all back together with the cleaned out air filter and see how she goes. ANy other tips? Will post an update soon. Thanks again fellas.
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post #14 of 45 (permalink) Old 06-26-2013, 02:14 PM
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Heyya,
With a air filter looking like that, your carbs will absolutely need a clean and I'd replace the inline fuel filter on the fuel line that runs from your tank to your fuel pump too.
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post #15 of 45 (permalink) Old 06-26-2013, 02:23 PM
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Yep, to remove the air box of the carbs, you need to remove the rubber bungs, put a socket on a long extender, shine a torch through one of the bung holes and feed the socket down onto the bolts, it's a really fiddly job. I found using a flexi drive extender for the socket easiest way to get the socket straight on as some of the bung holes are not quite lined up right to get a straight shot at the bolts.

And to the OP, don't rely on the carbs "looking clean". It's mainly the jets inside you cannot see that count.

Quote:
Originally Posted by AZXRider View Post
Easy boys. The filter is foam and sprayed with oil, like any other ZX filter. You need to get the airbox off, it's held on by some c clamps, you may need to access them through the plug on the top of the airbox dunno, maybe Christi or Mike will chime in, I've never mess with an H, J or K for that matter. Find a service manual, it will tell you how to get it off
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post #16 of 45 (permalink) Old 06-26-2013, 03:25 PM Thread Starter
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pic of the bottom of the airbox.. this poor bike.

Ive been reading on carb cleaning and it seems very complicated, I don't want to attempt it w/o a manual of some sort. I looked around some and came up short, anyone have a copy handy?
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post #17 of 45 (permalink) Old 06-26-2013, 05:10 PM Thread Starter
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Cleaned the air and fuel filters the best I could. Re-installed everything and got very decent suction from the fuel line this time. Put the tank on and SHE FIRED RIGHT UP :D

She still idles a little rough so I'm going to get some premium and some seafoam and see how that goes. I'm sure it needs a good carb cleaning but its not my bike so if the owner wants that done they'll have to get it done themselves as I'm not the person to do it...maybe someday after I've learned a little more.

Now, after I let her warm up a little bit, she seems to bog way waaay down (almost off) when giving it gas..any ideas here? Thanks for all the help..progress is being made :)
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post #18 of 45 (permalink) Old 06-26-2013, 05:28 PM
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Quote:
Originally Posted by jlkohel911 View Post

Now, after I let her warm up a little bit, she seems to bog way waaay down (almost off) when giving it gas..any ideas here? Thanks for all the help..progress is being made :)
Is this from idle with the choke off? If so then the pilot jets are clogged/dirty and need a good cleaning. You need to give the beast a full tune up. This would be spark plugs, oil and coolant change, all filters, spark plugs and check the valve lash as well as the aforementioned carb cleaning. Congrats on getting it running.

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post #19 of 45 (permalink) Old 06-26-2013, 05:35 PM Thread Starter
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Yeah, choke all the way off and from idle. I'm going to read some more on the jets and see if this is a project I can do myself...otherwise I'll refer her to my local small-business power-sports store. Thanks again and I will post an update as soon as I have anything worthy.
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post #20 of 45 (permalink) Old 06-26-2013, 05:39 PM
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That's because your pilot jets are probably clogged and dirty. Cleaning carbs isn't hard at all. You have to be patient and thorough, that's all. Until spring of 2012 I have never even touched carbs; now I can have my carbs off, cleaned and back on in less than an hour.

This three-part video on Youtube was very helpful for me to clean my carbs.


When you're done, you reset the pilot screws at the factory setting (most likely 2.5 turns out) and try it out. If your bike is stock or has a slip-on/bolt-on, that should be very close to perfect. Oh yeah, sync the carbs.
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