Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums - Reply to Topic
Engine / Exhaust / Cooling
\ From the radiator, through the case and out
the exhaust. If it has to do with the cooling,
engine or exhaust, discuss it here!

Thread: Bought a Vulcan with a non-running engine Reply to Thread
Title:
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:
 

Register Now



In order to be able to post messages on the Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Once registered, your User Name"cannot be changed". We can make exceptions within 7 days, but after that, it is set in stone.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










  Additional Options
Miscellaneous Options

  Topic Review (Newest First)
08-06-2011 03:05 PM
Cricketo99 The jets in the carb are 138 mains and 38 pilot. Will I be okay with these or do I need to step down a size?
08-05-2011 10:18 AM
centurynick i run 10w40 penzoil in my bike
08-05-2011 10:03 AM
Cricketo99 Also, on a side note, what type and weight of oil should I be using? Is regular diesel oil okay or do I need special motorcycle oil for the wet clutch? Like I said I know very little about bikes so bear with me.
08-05-2011 12:29 AM
Cricketo99 Okay thanks everyone! I will check to see what jets he had put in it when I am in there cleaning them out. I am going to check compression again once I get it running right to see how much it comes up. I am guessing those specs are for a warm engine correct? Also the gauge I used was one of those cheap "push in the spark plug hole" types so it is probably a little higher than that.
08-04-2011 09:42 PM
JM2001
Quote:
Originally Posted by Cricketo99 View Post
Got it running today! I don't really know if I changed anything or not but I took both the pickups off and inspected them. I then checked compression (cold obviously), got around 110 on the back and 120 on the front. Not really sure if that is bad or good. Put everything back together and after I primed it with ether she lit. She doesn't run very well but if I keep it above 2000 it will stay running. Also oil light stayed on until I loosened the oil filter to burp it. I am kinda thinking that may have been what happened in the first place. No unusual noises or anything. Looks like I'll be diving into the carbs next. That leads me to another question. I am a diesel mechanic but am new to the world of motorcycles. The PO had put on aftermarket pipes and he said he jetted the carb. My question is what jets should be in there with just the aftermarket pipes? Thanks to everyone it seems like everyone on this forum is very professional and helpful. On any other forum there would have been a fight already in this post lol.
Vance and Hines ( Cruzer Pipes ) recommend going one size up on the main jet which would be a 136.
08-04-2011 08:02 PM
OlHossCanada
Quote:
Originally Posted by Cricketo99 View Post
Got it running today! I don't really know if I changed anything or not but I took both the pickups off and inspected them. I then checked compression (cold obviously), got around 110 on the back and 120 on the front. Not really sure if that is bad or good. Put everything back together and after I primed it with ether she lit. She doesn't run very well but if I keep it above 2000 it will stay running. Also oil light stayed on until I loosened the oil filter to burp it. I am kinda thinking that may have been what happened in the first place. No unusual noises or anything. Looks like I'll be diving into the carbs next. That leads me to another question. I am a diesel mechanic but am new to the world of motorcycles. The PO had put on aftermarket pipes and he said he jetted the carb. My question is what jets should be in there with just the aftermarket pipes? Thanks to everyone it seems like everyone on this forum is very professional and helpful. On any other forum there would have been a fight already in this post lol.
Your cold compression test yields low readings at 110 and 120 psi.
Specs call for 129-199 psi with no more than 10 psi difference between cylinders.
Warming the engine before a retest may give you more satisfactory results.

Regarding carbs and re-jetting I am no expert, but this is what I can recall of what others have posted here.

Common consensus used to be that just changing out the exhaust did not require rejetting.
The intake was the restriction in the system, not the exhaust.

Then we had someone join the group who had a rule of thumb for re-jetting that was something like this:
Changing either the exhaust or the intake usually requires an increase of 2 jet sizes. Changing both would mean an increase of 4 sizes.
(Is one jet size 0.002"? ie. from 0.040" to 0.042" pilot jets , or 0.140"- 0.142" mains)

For every 2,000' gain in elevation ASL you drop one jet size.

So if I earshaved and put on afterarket pipes, I would add 4 jet sizes, then subtract 1 (or maybe 2?) sizes for my elevation of 3,500 feet ASL. YMMV

Others may have more specific numbers to offer.
08-04-2011 01:07 PM
DavesVulster lol, I know what you mean. I feel that Gordon is one of those guys you want to hang with. He always has good info and is gracious at correcting misinformation. You can find a ton of info on re-jetting carbs in the "carbs and fuel system" section of the forums. I removed my airbox and oem filters and found the info there to get the proper jets.
08-04-2011 12:51 PM
Cricketo99 Got it running today! I don't really know if I changed anything or not but I took both the pickups off and inspected them. I then checked compression (cold obviously), got around 110 on the back and 120 on the front. Not really sure if that is bad or good. Put everything back together and after I primed it with ether she lit. She doesn't run very well but if I keep it above 2000 it will stay running. Also oil light stayed on until I loosened the oil filter to burp it. I am kinda thinking that may have been what happened in the first place. No unusual noises or anything. Looks like I'll be diving into the carbs next. That leads me to another question. I am a diesel mechanic but am new to the world of motorcycles. The PO had put on aftermarket pipes and he said he jetted the carb. My question is what jets should be in there with just the aftermarket pipes? Thanks to everyone it seems like everyone on this forum is very professional and helpful. On any other forum there would have been a fight already in this post lol.
08-04-2011 10:15 AM
DavesVulster
Quote:
Originally Posted by OlHossCanada View Post
I don`t like to contradict you Dave, but I believe the plugs should fire on every rotation of the rotor magnets past the ignition pickup coils. Not sure that it matters if there is a waste spark during the exhaust stroke though.

The vn750 does not have a magneto, but an electronic ignition system that is not adjustable for timing. Timing can be checked with a timing light though, by taking off the stator cover.

A compression test of both cylinders will help confirm or eliminate some possible causes of the symptoms I think.
No problem at all Gordon, that's what this forum is here for... and I usually learn something from your posts to boot . It does make sense after thinking about the reed valves that there could be a need for a spark on exhaust to burn the unused gas on the way out. Was just putting some ideas out there to look for / discuss, maybe too much. Might confuse . Sorry if I did. Anyway, As usual I appreciate your knowledge and the knowledge of others and of course the willingness to help fellow members.
08-04-2011 10:06 AM
Cricketo99 Okay I figured by looking at the pickups inside the stator cover that it would have to fire every rotation, much like a lawn mower or other small engine. Unless somehow the IC or whatever it is called somehow knows when the compression stroke is and only tells the coils to fire then. Can I check the timing with a light without the engine running. The only thing I could find in the manual it says the engine has to be running at a certain rpm and the marks will line up. If I check it with a light with just cranking should the marks still line up?
This thread has more than 10 replies. Click here to review the whole thread.

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

 
For the best viewing experience please update your browser to Google Chrome