Kawasaki VN750 Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter #1
I am having issues with my 750. I got the bike(1990 VN 750)a couple weeks ago from a "friend". Its my first bike and I was thinking it was going to be magical. I was wrong:doh:. It lacked alot of power. I had many suggestions as to what it could be but nothing worked. I put some seafoam in the tank and then all hell broke loose. After that it started chugging and lurching. Then it died. Now, It wont even idle (when I can get it started). When I do start it the throttle has to be wide open. It usually takes a couple of tried to do this. It picks and chooses what day it wants to start up. Today i got it started (first time in 2 days) and I had alot of white smoke for about 10 minutes and it started back firing. I have tried carb cleaner but it hasn't worked after 2 cans. :blah:. Now I am desperate. I love riding but I can not right now with the problems I am having. Please help.
 

·
and the Adventure Cycle
Joined
·
6,141 Posts
Are you mechanically inclined?
Do you think you can handle pulling the carbs?

Of course you can!!
More than likely the carbs and internal parts need cleaned. Maybe the fuel tank & petcock also. Have you taken a look inside the tank to see it's condition?

The Seafoam was an excellent place to start. The carb cleaner...maybe not.
Some carb cleaners can have an adverse reaction to plastic parts in the petcock & carbs.
A good carb cleaning seems to be what you need.

Also, did you try changing the plugs at all?
What about the air filters? Are they clean?
Did the smoke smell like fuel, as in a flooded condition?

Oh, and welcome to the forum
 

·
Registered
Joined
·
30 Posts
Discussion Starter #3
I did pull the tank and cleaned the screens. I removed alot of junk from the tank as well. I have changes the plugs and it helped a little before it took a dive. And I do smell alot of fuel in the smoke. there are K&N type filters on it and they are clean.
 

·
Premium Member
Joined
·
3,505 Posts
White smoke is usually an indication of coolant getting into your cylinders and burning off; but the fact that you're smelling fuel suggests otherwise. Your carb floats may be stuck, leaving the engine kind of overwhelmed with gas (which can leak out any number of places)...got any visible leaks at all, or just the smell? Also, when you changed the plugs, were they wet with gasoline?

As folks here have drilled into my head, you need three things to get the bike to start and idle: spark, fuel, and compression. Easiest thing is to see that you have spark at all four of the new plugs (could be a problem with a wire or two); then check the fuel flow - an air leak can severely impact the ability of the gas to move nicely through the system; and finally check the compression - there are tools you can use to check that, or you can pull the spark plugs and try the ol' "I guess this finger is an extra" test. More on that anon.

:)
 

·
Chucklehead
Joined
·
1,050 Posts
"I guess this finger is an extra" test.

:)
Now you have me curious .... never heard that one. But you're right about the whitew smoke, usually coolant with a "sweet" smell unless you have straight water in the system (naughty naughty but could be worse) Could also be water in the fuel, flooded smoke tends to be black, oil smoke is blue, or possible the carb cleaner is the source of the white smoke. I would say determine the source of the smoke and we can go from there. Check the coolant level and make sure you aren't losing any internally.
 

·
Premium Member
Joined
·
3,505 Posts
I can't remember who suggested I do this, but it worked. I wanted to check the compression in O's cylinders. Pulled both spark plugs from one of the cyls, and moved the wires waaaaaaay far away from my person. Put one finger over one of the spark plug wells and cranked the engine. If you have compression (not necessarily enough, but compression), your finger will kinda blow off the hole that it was covering. Or maybe it didn't blow off; maybe I just got scared that I'd accidentally used a highly useful digit and yanked it off the engine as soon as I felt the pressure. At any rate, even if one loses a finger with that method, the good news is that you'll know whether or not there's compression in the cylinder! :beerchug:
 

·
Registered
Joined
·
30 Posts
Discussion Starter #8 (Edited)
I have noticed a little bit of fuel collecting on the outside of the carb. I had nearly a full tank when I added the seafoam. My coolant level is fine. No changes there. Its not a sweet smell at all like coolant and its white smoke which may be the carb cleaner burning off and it just an overwhelming gas smell. Every time I pull the plugs they are wet with fuel. The engine also makes a completely different sound when I crank it without touching the throttle. It also backfires alot when I try to crank it.
 

·
Premium Member
Joined
·
812 Posts
Sounds like you're just pouring the gas through your engine. The carbs need a rebuilt. Until you pull them and clean everything out and replace whatever is broke, you're just not going to have any fun.

How long has your "friend" had the bike in storage with gas in it before you bought it? That old gas could have gunked up and clogged everything.

Gemguy
 

·
Registered
Joined
·
30 Posts
Discussion Starter #10
Just went out to my bike after sitting all day. It fired right up. It idled just fine. I tried a few things that others have mentioned("burping" turning petcock to off and letting it run out of gas and recranking it and doing it all over again) Don't know what it was for but I tried it. While that was going on it backfired a lot. Minimal smoke this time. As soon as I backed it out of the carport to try it, She died and would not re-crank. I mean it idled great for about 15 minutes that as soon as backed up it died.
 

·
Premium Member
Joined
·
4,054 Posts
It really sounds like you're moving stuff through the fuel system as it tries to clean its self out. Probably your slides were stuck, and maybe they popped loose but now you've moved some more crud through and clogged something else up. I don't think it's totally out of the question that the seafoam bath might end up clearing it up, but your situation sounds pretty bad and might still end in a good carb pull and cleanin. If you've got the time, as long as you're still sporting a good amount of seafoam in the gas mix, each time it sits, it's going to do some more cleaning. Believe me, we've seen some real miracles performed by seafoam. Now, if you're in a hurry, pulling them is probably the only quick way to go.
 

·
Registered
Joined
·
30 Posts
Discussion Starter #12
I will be gone all weekend. So it will sit up for probably 3 days without cranking. I have a pint of seafoam in it right nowbefore I topped it off last. So there is quite a bit of it in there. I will see on monday morening when I finally get a crack at it again. If that dosent help I will be pulling the carbs monday afternoon. Thanks for the help fellas'
 

·
Premium Member
Joined
·
136 Posts
you need three things to get the bike to start and idle: spark, fuel, and compression.
This is somethign I fight everyday. everyone has been taught this, and its true...To a point.
All 4 cycle gasoline "Otto" engines need the same 5 things in order to run. It doesn’t matter if it’s injected, carbed, whatever. These principals will help you diag a Crank/No Start and misfire concerns on your Vulcan, car, Lawnmower, etc.

1) You need air. You have to have air coming in, but also leaving the engine. Plugged air filters, plastic bags sucked in, clogged exhaust all can cause a no start or misfire.

Visual inspection of your air filter will be your friend here, also check the plumbing to the engine. A vacuum gauge is an excellent tool to quickly asess your air, among other engine concerns. They are cheap and available anywhere.

2) Fuel. You need gasoline. Not only the right amount, but you must atomize the fuel. Atomizing is basically creating a mist. Picture trying to start a 2x4 on fire, and starting sawdust on fire. Same idea.

Carbureted engines, engine vacuum is a big player. Most Fuel concerns on a carbed engine get diagnosed as an elimation of the other 4.


3) Spark.
You have to have spark. This is very easy to confirm. You are looking for a big, bright blue spark while cranking.

http://www.thetoolwarehouse.net/shop/LIS-50850.html


This tool works just nifty. If the spark is big and blue, and pulsing…It’s safe to call the ignition system good.

Spark plug design will have an effect. Some people like Voodoo Magic spark plugs, and if it works for them great. For a diagnosis baseline, a smart mechanic will install OE spec spark plugs. It’s not unusual for the simple act of installing the correct spark plugs to cure misfire and no start concerns.


4) Engine timing. The air, spark and fuel need to come together at the correct time. Timing can be confirmed with a timing light in most cases.

Engine timing CAN be checked with a timing light on a Vulcan, but its messy, and if your timing is off, there is little you can do about it. Its not adjustable that I know of, and usually means a chain has jumped.


5) Compression.

Finally, you need compression. A rule of thumb is there should be a less then 10% difference from the highest to the lowest reading. The actual reading isn’t as important as this %10 spread. Again, the service manual with have the procedure and specs.

http://www.sears.com/shc/s/search_10153_12605?keyword=compression

Any of these will perform the task just fine


Every no start and drivability problem in the history of gasoline 4 stroke engines has been cause by one or more of these 5. Every one! Performing the tests to confirm what you have and what you don’t will save you time and lead to a more accurate diagnosis as you can focus on what is not working correctly. (Fuel, Spark,Etc)
I would strongly encourage checking ALL 5 to get a good big picture view of what’s going on. Finding missing spark for example and stopping there in your testing can cause problems later in the diagnostic procedure.

I also cannot overstate the importance of a repair manual as a test and spec reference. Without knowing what specs you are looking for, and how to perform the tests…Why bother performing them, you don’t know what you are looking for.

Don’t let yourself get overwhelmed in the electronic gee wiz-ness. An engine is an engine, and these principals apply to all 4 cycle gasoline engines….Airplanes, lawnmowers, cars, motorcycles, etc.
 
1 - 13 of 13 Posts
Top