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Discussion Starter #1 (Edited)
Hi.
First of, i am an idiot. I purchase this bike out of compulsion and now i think i have a problem. I am hoping that someone could help me out. It is an 86 vn750 with 14k on it. All inputs are appreciated.

Problem: the front engine (cylinder) seems to produce less power than the rear. Maybe 60 percent compare to the rear.

From the sound and exhaust air exit, i noticed that the rear engine sound louder and push more hot air out of exhaust pipe. Is this normal on a vulcan 750 to have one cylinder produce more power than the other? I have custom home made drag pipe run along both side ( just like V&H cruzer), so the front engine has a longer pipe. Would this be a factor?. How could i tell if this weak combustion caused by carbs or valve?

I have brand new sealed batteries (agm), all new ngk spark plugs ( dpr7ea-9). When i star it, it seems like the front engine pick up first and then the rear catch on. It does seems like it run great and smooth in all rpm. Steady accleration all the way up to 70mph. however i dont know how a good working vulcan 750 run like. RPM hand does not stay steady at a steady speed, does this need carbs sync?

Potential causes:
1. Carbs need clean up or sync. I noticed that the gas tank is rusted when i fill up gas. So could this clog carb of the front engine cause it to give less fuel?. The air/mix screw still has factory lead seal so i assume both carbs are in original setting.
2. Ignition coil. I have tested all coil and it does give sparks. could i have bad coil?
3. bad or damage valve? . This is where it get over my head. I am a newbie.
4. Head gasket? i noticed some liquid come out of the right pipe ( from front engine). I am going to fill up anti-freezer tomorrow and monitor to see if i lost any anti-freezer.

All the experts, please help me out. Oh, English is my second language. Please forgive me if i make no sense. I try my best to explain the stituation. Thank you so much.
 

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Newb with a Bullet!
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Sounds similar to what I am dealing with. I am newb-ish myself, but for sure the rust in your tank is not doing you any favors. I think everything you are describing could come from gummed up carbs full of rust and gunk.

I just derusted my tank with muriatic acid, cleaned out my petcock and carbs. It helped TREMENDOUSLY although it's still not 100%. I think I might have missed some gunk so I'm going to clean out again.

Like you it seems most of my problem is in one cylinder. In my case it's the rear (left). It ran super strong just a couple of months ago when I parked it due to a fuel leak so I doubt anything internal is wrong with my cylinder (valves, etc.) It's almost certainly something more basic than that- and given that I have proven that gunk has been a problem in my carbs from my rusty tank it makes sense to keep barking up that tree until it has been eliminated as a cause.

If I were you I'd start there- derust your tank, clean out your petcock and carbs and see if it helps. I bet you it does!

Keep us posted on your progress!
 

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Discussion Starter #3
Thanks Krebsne. I am hoping my problem is in the carbs. And i think i'm gonnga star from there first. I'll try to take it out and clean it. Any suggestion on take out the carb?

Btw, good job on the rattle can paint job. I have learn alots from it.


John
 

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Newb with a Bullet!
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Are you earshaved? I took my carbs out last night and cleaned them and I was SO GLAD I earshaved just so I could get those buggers out. Taking them out w/ the stock air breather system is NO FUN. I did it once, years ago. All I remember is how hard it was!

So someone else might have to chime in w/ advice on that. I know it's difficult. Even airshaved mine weren't super easy to get BACK IN, but getting them out at least was easy.
 

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Hi and welcome to the group! You say your tank is rusty? If so, you obviously have rust and crud clogging up your carbs and fuel system. I would remove the carbs and give them a thorough cleaning. While they're off, you need to get rid of the rust in the tank. No way do you want to re-install the clean carbs under a rusty tank. You will be wasting your time cleaning the carbs otherwise. Good luck!
 

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Simple Solutions
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what kinda fuel u runnin .... use regular double check all grounds... grab a couple of cheap fuel filters (one if u just put it on the main line ) this is to prevent any more residue from forming in the carbs. like suggested clean the carbs and tank there is a great link in vers. for rusty tank using a batt charger and spa cleaner (ph +)... (get the details its a worth while to do it this way cheap and very effective stay awayu from TANK LINERS.... I dont think your prob is internal... where do u live (elevation ) and where did the bike come from (has it always had prob at your current elevation) u may not have answers to that question but it may help us in diagnoses.lastly pull the air cleaners and check for debris i had a rats nest in my air cleaner when i got my bike... Last but the most important get a can of "seafoam" and as directed put a shot or 2 in the tank and a swallow in the crank case ride for 50 - 100 miles.... do this before anything else( i almost guarantee this will work if the prob is carb related this is no substitute for cleanin the carbs but it works phenomenally... keep us informed u will be happy with your purchace shortly

other recomendation is ngk iridium plugs instead of plane ngk...
 

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On His Lady Vulcan
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As stated prior to my posting, clean the tank and carbs. Also I seen that you mentioned that you installed drag pipes. If so you NEED to adjust your pilot screws on each of the carbs, start with 2 3/4 turns out and go from there. So yes, that means that you will have to remove those lead caps. I am willing to bet that will cure what ails her.


Peace:beerchug:
 

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Linkmeister Supreme
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Welcome to the group bikeronbudget. Fill out your profile and let us know where you live. The "Seafoam" fuel additive suggested by seebeeare is only available in North America it seems. You may have to find something similar where you live.

Here is a link to krebsne`s thread about using acid to clean out the inside of his tank: http://www.vn750.com/forum/showthread.php?t=12009

Another link to verses for getting rust out of tank:http://www.vn750.com/forum/showthread.php?t=1124

Using electrolosis to to seal rusty tank: http://www.vn750.com/forum/showthread.php?t=1152

A link to Crobins picture gallery with many carb cleaning and labeling photos: http://www.vn750.com/photopost/showgallery.php?cat=500&ppuser=962

I hope some of this helps you get the bike running well .
 

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Welcome. I installed small diameter (about 3/4 inch), clear, in-line fuel filters on the lines from the petcock to the carbs. Keeps crud from getting to the carbs in the future, and I can tell if fuel is flowing and if junk is coming out of the tank.
 

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Discussion Starter #10 (Edited)
Thank you so much for welcoming me. I am overwhelming and greatly appreciate all advices.

So from recommedations, this is what i should do:
1. I should start with seafoam first.
2. Adjust air/feul mixer to 2 3/4 turns
2. If problems still persist, i should clean or replace fuel tank, clean petcock.
3. And if it is still there, carbs clean up ( big job)
4. Must be gasket or head valve

am i right? thanks
 

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Discussion Starter #11
Welcome. I installed small diameter (about 3/4 inch), clear, in-line fuel filters on the lines from the petcock to the carbs. Keeps crud from getting to the carbs in the future, and I can tell if fuel is flowing and if junk is coming out of the tank.
There are no room for inline fuel filter unless i got new tube and extend the fuel line. btw, where do you mount your inline fuel filter? thanks
 

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On His Lady Vulcan
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1,647 Posts
Thank you so much for welcoming me. I am overwhelming and greatly appreciate all advices.

So from recommedations, this is what i should do:
1. I should start with seafoam first.
2. If problems still persist, i should clean or replace fuel tank, clean petcock.
3. And if it is still there, carbs clean up ( big job)
4. Must be gasket or head valve

am i right? thanks
Tap...Tap...Tap... is this think on???


You NEED to adjust your pilot screws if your running str8 pipes like you stated. Right there is about your biggest problem. Good luck.
 

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Discussion Starter #13
Tap...Tap...Tap... is this think on???


You NEED to adjust your pilot screws if your running str8 pipes like you stated. Right there is about your biggest problem. Good luck.
hehehehe...thanks wkrizan. I'll try that first.

1. adjust air/fuel to 2 3/4 then seafoam to clean up.
 

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On His Lady Vulcan
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hehehehe...thanks wkrizan. I'll try that first.

1. adjust air/fuel to 2 3/4 then seafoam to clean up.
By George I thinks hes gots its


EDIT: Keep in mind that you might have to play with it a little, if youre still running too lean you may have to go 2 1/2 turns out or 3 turns out if your too rich. With the screws set to factory and youre running drag pipes your bike will run like s.h.i.t.
 

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There are no room for inline fuel filter unless i got new tube and extend the fuel line. btw, where do you mount your inline fuel filter? thanks
The filters go on the lines from the petcock to the carbs. Just cut out a section of the existing fuel lines the length of the filter body, slide clamps over each end of the cut hose, insert the ends of the filter into the shortened hose, and place the clamps on the hose where the nipple ends of the filter are. The best time to mount them is with the fuel tank removed because you have more room to operate. However, they can be installed with difficulty with the tank mounted if your hands aren't too big. As mentioned in my earlier post, the filter needs to be no larger than 3/4 of an inch or about 2 cm. There isn't room for anything larger. Not sure what is available where you're located.
 

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Discussion Starter #16 (Edited)
Thank you all so much for your help.
This morning i removed the lead cap and adjust the pilot screw for the front cyclinder to 3 (left side) and the rear cyclinder to 2 1/4 (right side). And I also put seafoam 1/3 in gas tank, 1/3 in crank case (oil) and a litttle in vacum port on both cabrs. I let it sit for 30 mins and start it. Took about 5 mins for the smoke to clear.
I noticed the front cylinder improve a little bit. A little louder and push more air. But still no way as the same bar as the rear cyclinder. So what else should i look for now? or should i do now? Thanks.

A few pics of my bike. She is old and i hope she will hold :).

Here it is bone stock when i got it.



And here it is today






 
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