1500 Classic Engine Vibration [Archive] - Kawasaki Vulcan Forum : Vulcan Forums

: 1500 Classic Engine Vibration

09-14-2009, 02:38 PM
Purchased a 99 Vulcan Classic 1500 a few weeks ago. It has 39K on it. Starts very good but choke must be used for 1st start. Seems to have too much engine vibration. After it warms the vibration is still the same. This is a vibration that is constant just sitting still.
Only known mods are Vance Hines 2into1 pipes, and a hyper charger. I ordered a full factory exhaust system and just finished installing it. (Man is it much quieter.) Removed the carb to check the jets and they are stamped factory. 135 & 45, so I don't think anything was done there. Checked the mixture screw and it was out 3 turns, so I turned it in one.
I removed all 4 plugs and the two rear cylinder ones were very black as if running extremly rich. My milage is only about 25. Installed new plugs but that did not make a change.
I am by no means a bike mechanic, but I do know engines. So if you need more information to assist in a diagnostic, please ask.

Thanking you in advance for any suggestions and glad to be a part of this forum.

09-14-2009, 08:57 PM
Vibration probably is from a misfire. I have some questions:
1. Start OK, hot/cold?
2. Idle OK, hot/cold?
3. Backfiring at anytime?
4. Drive along oK, hot/cold?
5. Any other driveability issues, no matter how minor?
6. Back plugs...if you clean them, do they soot up right away?
6. Any other issues, even if seemingly unrelated?

Post back.

09-14-2009, 10:02 PM
Engine starts good, must choke when cold, but otherwise starts right up

Idle is fine

No backfires at all

Only driving problem is a dead spot at very low throttle. picks up as soon as given a little more throttle.

No other driving problems other than vibration, which disappears when clutch is pulled it, indicating it is engine vibration.

New plugs were sooted up with less than 20 miles of driving after installation

Only other issue is extremely poor gas mileage.

Thanks for your response.

09-15-2009, 01:02 PM
The condition, as you describe, is typically an off-idle lean condition, but the black plugs do not support that.
One thing that you can try is to swap the two coils with each other to see if the problem moves. Check for a full 12v at the wire that goes to both coils. Also meter the plug wires for continuity.

Post back with your findings

10-05-2009, 04:01 PM
Well I am finally back with the results of my most recent test & inspections. Here is where I am.
First, I could not stand the loud noise from the Vance Hines 2 into 1 pipes that were on the bike when I purchased it, so I found & ordered a complete factory exhaust system and changed that out. (Now I can once again hear), but that had no effect on the vibration problem. Next I checked the voltage at the coils and did resistance checks and they are both OK. Today I removed the carb, disassembled and cleaned. Both jets are stamped FTC for factory installed, a 142 & 45. Cleaned both with tip cleaners, checked float level and everything else. All OK. Reassembled and started. Engine idles fine but as I begin to give a slight amout of throttle, vibration begins and continues up to the high RPM range. When trying to ride is very uncomfortable as it vibrates all the time.
New observation: When I first started engine before connecting crankcase vent lines to air filters I noted a lot of pressure & vacuum from these hoses. After connecting all lines and putting everything back together, I started engine and unscrewed the oil fill cap. There is pressure, vacuum as if I have a direct cylinder leak into the crankcase. I understand there is a decompression feature on the front cylinder for cranking purposes. Could this be stuck in an open position? Is it supposed to close after starting?
Thanks again for any suggestions.

10-05-2009, 04:24 PM
You have done some first class work in trying to track down the problem.
Decompressor holds the exhaust valve open a smidge, so will not contribute to crankcase huffing and puffing, which, depending on how much, is normal for an engine.
You should do a leak-down test just to make sure that the engine is sound, mechanically, although, the good idle seems to indicate it shouldn't be too far off.
A real close examination of the plugs would be in order to try and narrow down which cylinder might be the offender, if indeed there is one.

Post back with your results

10-05-2009, 04:58 PM
I just pulled the plugs for inspection and this is what I found.

Right & left rear are very black with soot. Wiped off with rag and reinstalled.

Front plugs have a small amount of soot but mostly grayish in color. Wiped off and reinstalled.

As noted earlier these are new plugs with maybe 100 miles on them.

10-05-2009, 07:36 PM
The black rear plugs speak of a mis-fire in that cylinder. Did you try swapping the coils?
Also, try measuring resistance of coil wires. I do not know what the exact specs. are for your bike, but they should all be very close to each other.
Another thing to try - Pull one plug from rear, ground against engine and check spark.
It should be fat and blue, not weak and yellow. If in doubt, check it against one of the front ones.

Post back with your findings

10-06-2009, 11:37 AM
This morning I removed both coils and did resistance test on them. The results were almost the same on both, 2.6ohms on primarys and 22.4K on the secondarys. According to my manual that is right in the middle of the recommended range for both.
I did a spark test on each wire using a new plug grounded to the frame and the spark was very blue and good at all 4 test.
Started bike and let warm up and have noticed if I gradually increase fuel vibration increases, but when I reach a high RPM range it seems to smooth out. I am beginning to lean toward a burnt valve. As I said earlier it had V&H pipes on it when I got it and no rejetting had been done. I do not know how long they were on it but the bike does have 39K miles.
I do not have the correct metric adapter for my compression tester. I will try to pick one up today and do a compression test.
What are your thoughts on these results so far?

10-06-2009, 02:18 PM
Results of compression test were:

Front cylinder was a consistent 120 for 3 test. I found this confusing since the manual states it should be between 50 & 80 because of the automatic cranking compression release.

The first test of the rear cylinder was 125, second test was 65, third and there after resulted in 90. The manual states it should be between 120 & 150 for the rear.
Well, I am just as confused as I was before the test.

10-06-2009, 09:43 PM
That is why a leak down test is better...eliminates the added involvement of the compression release. In fact, eliminates all confusion as to specs, results, etc.
If the leakdown test comes out good, there may be a possibility that there is a problem with the comp. release for the rear cylinder.

A leak down test will show up any leaking valves, for sure.

Post back.

10-07-2009, 11:30 AM
The dredded leak down test has been done & the results are in:

Front cylinder had hardly any noticeable leakage. Less than 5%

Was unable to do a test on the rear cylinder as the air was flowing out
the muffler as fast as I could put it in. Tested several times to insure TDC of piston & got the same results. :(

Either a burnt exhaust valve, or defective Auto compression release

10-07-2009, 07:59 PM
You trouble shot the problem using the correct test equipment and were successful in pinpointing the tender spot. Good work! Much better than just throwing parts at it, lightening your wallet in the process and bike still runs like crap.
The easiest to check will be the compression release; just pop valve cover (if that can be called easy), otherwise head has to come off. If it needs a valve job, it might be wise to do both heads.
Just as an add, test at "both" TDC's to be sure you got the correct one.
Good luck and post back to tell us how you make out.

10-07-2009, 08:15 PM
Man that really sucks big time, i hope you can rectify the problem ASAP.
Good luck

10-07-2009, 09:04 PM
I borrowed a friend of mines camera today and went inside of the cylinder with it. I could see what appears to be a burnt side on one of the exhaust valves. There is a tremendous amount of carbon build up on top of the piston and the valves.
Will begin disassemble for dropping the engine first of next week. As I have never done this before it may be a slow process, but I will keep you guys posted as to the results of my findings.
Thanks for the help in diagnoising the problem.

11-10-2009, 01:45 PM
As I stated in my earlier post, I thought i was going to find a burnt valve in the rear cylinder. Not to be. In fact I could not find anything wrong with either head. I have checked all valves, springs, seats & retainers. Miked the cam lobes, check the auto compression releases and have not found any problems. Checked timing chain tension and gears.
Reassembled and it runs exactally as it did before the taredown.

I even second guessed myself about the timing and removed the engine again to verify that the timing was correct, which it was.

Engine still starts up fine and will idle, but when I try to give it fuel it dies. If I feather the throttle I can get it to continue running but it is very rough. Will usually backfire thru carb and die.

I just did another leakdown test since I have found how to find TDC for the front & rear and there is absolutely no leakage.
I am convinced it must be a timing or spark problem. The coils have 12.3VDC on cranking but I only have a bright yellow spark accross the plugs. Resistance is at spec, for both coils. So I wonder if it could be the throttle position sensor, which signals the advance for timing, or could it be the ignitor?

11-10-2009, 04:29 PM
First, I wonder why it failed leakdown test first time?
Second, you now mention backfire through the carb, which you did not mention before. Is this something new?
Carb backfire usually is caused by lean condition, but can also be leaking intake valve, timing and vacuum leak. In your case, I am leaning away from the last three if it idles OK, as they will show up at idle too.
This bike has a throttle position sensor?

11-10-2009, 04:48 PM
I suspect I did not have the piston for the rear cylinder @ TDC the first time I did the leak-down test. The back firing is new, although I do not have the air filter on as before and it is very noticable. Yes, it has the sensor on the side of the carb with a 3 wire cable attached to it. Might add that I have connected a vacuum gage and it is all over the scale. Not familiar with how much or steady it should be on a V-twin.
Just removed the ignitor module, but do not have any test specs for it as my manual does not cover this model.

11-10-2009, 05:44 PM
The throttle position sensor will modify the pre-programmed ignition curve in the ignitor.
What it probably does is add a little advance when engine speed is high and throttle closed and take out a little advance when engine speed is low and throttle wide open. I do not think that this is your problem, but it should be connected.
I would like to re-cap:
1. Leak-down test passes, both cylinders.
2. Starts and idles OK.
3. Open throttle, starts to backfire through carb and dies.

This is pointing to a carb problem of some sort. Before you tackle ignitor, take a look at this. You might spot a problem:


11-10-2009, 05:50 PM
Just as an add, take some aerosol carb cleaner and spray around intake manifold connections while bike is running just to check for any vacuum leaks. If it picks up RPM, you have a leak.

11-10-2009, 06:46 PM
Your re-cap is correct.
I have been thru the carb several times and checked every possible jet & orfice to insure they are clear. If there is a problem with it, I cannot find it. Will try the spray tomorrow and see if that has any affect.

11-11-2009, 02:20 PM
I have sprayed around the carb, intake & manifolds where it bolts on with no noticable effects. Removed carb again, disassembled, checked every orfice, & diaphram and cannot find anything wrong. Started up and idles fine but runs extremely rough when throttle is advanced. Release throttle to return to idle and runs smooth.

11-11-2009, 04:16 PM
More questions:
1. Is pilot screw at or near factory adjustment or did you have to add extra turns to get it to idle?
2. Still popping through intake when you give it throttle?
3. Did you check ignition timing with a timing light?
4. Connect timing light to each plug wire in turn and watch as the miss starts. Does the light start to jump all over the place or still stay regular with no misses?

11-11-2009, 04:43 PM
Pilot screw is @ 2 1/4 turns out.
Yes it is still popping thru carb when given gas
Have not checked timing with light. How would you go about this since it is fixed thru the excitor? Where would you aim the light? My stator cover has an alightment hole for the timing, but I doubt there is enough room to see the marks with a light. Please advise.

11-11-2009, 05:56 PM
Generally, you take off the alternator side cover and possibly a plug and you will see the rotor. Connect timing light to front plug wire, start and shine light into hole. at idle, timing mark "F" should align with notch in access hole. Do the same with back cylinder, should align with "B". I cannot guarantee that your bike is exactly like this because I have not seen every bike in the world, but should be along these lines. A shop manual would give you specifics if these instructions do not match.
Rev the bike a little and marks should advance.

11-11-2009, 06:10 PM
OK, I understand now. Will give it a try tomorrow or might have to be Friday and will get back to you with results. Thanks

11-13-2009, 05:27 PM
Today I borrowed a timing light and did the test. Set the idle at a steady 950 rpms. Connected first to front cylinder and timing mark was all over the place. Would see it on F mark and it would move up then down then out of sight and come back to center and repeat. Connected to rear cylinder and the same result. Would see R mark and start moving all around. RPMs were remaining steady.
Also removed pilot jet and drilled out next size up and back-firing and popping has stopped. When given more throttle now it does not pop and die, but is still running very rough. I now think this may be attributed to the irregular timing.
Is there a test that can be done on the ignitor to determine for certain that it is defective? They are quite expensive.

11-13-2009, 08:49 PM
Finally, something to sink our teeth into. Timing should not jump around.
Usually, it is the pick-up coils that are failing if the timing is erratic. About the only test a person can do on them is a resistance test, without special equipment (unless you have access to an ocilloscope).
You will need to have a shop manual to perform the tests on the pick-up coils.
One thing to check is make sure that all pick-up coil connections are clean and tight.
I suppose you could buy the coils on spec., that would be up to you.
I would not have made any carb modifications until this problem was sorted out; it may "cover up" other symptoms.

Post back.

11-13-2009, 10:19 PM
Installed a new set of pickups about a week ago. They had no effect so I didn't mention it. Even before I replaced them I did the test proceedure and the resistance was within factory specs.

11-14-2009, 10:55 AM
Crap. There goes that idea. Before jumping on the ignitor, every other possibility has to be ruled out.
Just to go over again.
1. Plug wire and caps are good. If they have gone high resistance or open internally, can cause problems. When engine tries to speed up, plugs are a little harder to fire and instead of jumping spark plug gap, it finds another convenient place. Sometimes looking when it is dark, you can spot a telltale flash.
2. No cross-fire between plug wires.

There is a possibility that this could be vibration related. With bike idling:

1. Tap on ignitor and junction box with the butt end of a screwdriver.
2. Tug, tap and wiggle all connectors on above.
3. Tap and wiggle on ignition key, handle bar switches and their harnesses.
4. Does the neutral light flicker or go dim when it starts to sputter?

12-07-2012, 11:06 PM
Hey Bandit, did you find the answer to this problem? It sure sounds like the same one Im having.

12-09-2012, 09:02 AM
There were two things that dramatically helped. One was rejetting the carb. I was not getting a balanced fuel flow.
The other was that the aftermarket pipes (V&H pro pipe), was installed with the bracket bolted directly to the frame. I installed another (fabricated) bracket with a rubber isolation dampening washer.

12-09-2012, 11:36 PM
Thanks for that. I have tried isolating the pipes with new rubber washer, no change.
I have the same rear plug carbon issue as you. The vibration on mine happened gradually over about 1000km's. Sometimes it's worse and at certain revs (cruising) on a good day I cant feel it until I throttle on.
I dont want to do what you did and pull the engine for nothing. The bike runs well, has a flat spot as I throttle from idle and sometimes backfires(more of a gasp). My concern is that under load, say 100kmph and throttling on, the whole bike vibes badly and there's a loss of power. Particularly noticeable in head winds. I've checked everything you have as well. Frustrating coz it ruins my rides.

12-10-2012, 09:28 AM
On a two cylinder engine, it is critical that each cylinder pulls its share of the load or power loss and vibration will result, even if it is intermittent.
Remove the plugs and post back with "exactly" what you see. A picture would be even better.

Ken Means
02-03-2013, 03:25 PM
I'll give you my opinion and that is only as good as the air I breathe. It sounds like you have a bad hydraulic lifter. If it is and it did like my old bike, the rear cylinder would not clear the gases if it is the exhaust side that is bad, and it will build a huge carbon deposit on top of the piston and throw it off balance.This causes it to run ok, but just not quit right and it vibrates. If you pull the top covers off the heads and push down on the cam end of the rocker arms, you should not be able to compress it with your finger. If it does, you will have lots of fun to replace the lifter on that rocker arm. My engine has done this twice from having the s&$t rung out of it. The lifters are not to hot in my books? What happens is the vale opens late and closes early and not clearing the charged gases. The other exhaust valve is probably doing fine in the same cylinder. It sure throws thing out of balance as far as I have experienced.

02-03-2013, 05:48 PM
Hey Ken, thanks for that very interesting info. It sure makes sense to me that it could indeed be the issue.
I have not seen anyone else come up with that diagnosis even though they suffer the same symptoms.

You say it has happened twice, did you have to remove the engine to change the lifters? How many miles had the engine done? Do you think it causes damage to leave it? Do you know of any aftermarket(and better quality) lifters?

Sorry for interrogation but Im just excited to find someone that has had the issue and solved it!

02-03-2013, 10:04 PM
I'll give you my opinion and that is only as good as the air I breathe. It sounds like you have a bad hydraulic lifter. If it is and it did like my old bike, the rear cylinder would not clear the gases if it is the exhaust side that is bad, and it will build a huge carbon deposit on top of the piston and throw it off balance.This causes it to run ok, but just not quit right and it vibrates. If you pull the top covers off the heads and push down on the cam end of the rocker arms, you should not be able to compress it with your finger. If it does, you will have lots of fun to replace the lifter on that rocker arm. My engine has done this twice from having the s&$t rung out of it. The lifters are not to hot in my books? What happens is the vale opens late and closes early and not clearing the charged gases. The other exhaust valve is probably doing fine in the same cylinder. It sure throws thing out of balance as far as I have experienced.

And you experienced no knocking or tapping?

I do not think that the carbon was the problem but the fact that the cylinder was not pulling its share of the load that caused the vibration.

02-03-2013, 10:10 PM
No knocking but tapping on one lifter.

Ken Means
02-04-2013, 12:19 AM
Yes with some near surgical techniques and enough knowledge of the valve terrains it can be done. But you have to pull the left stator cover or the right clutch cover to expose the crankshaft end and also pull the engine motor mount bolts to lower the motor in the frame enough to remove the valve cover bolts on the rear cylinder. Usually it is the rear that fails because of the extra heat the rear cylinder gets. I have the more radical cams of the first 3 year model engines that was produced and a heavy throttle hand. This spells failure as a rule of thumb. First, if I where you try a piston soak treatment to remove the carbon from the top of the piston before you tear down the engine! Also run some Sea Foam in the gas for several miles to decarbon the valves. Our gas here has alcohol at 10% to help f&%k up our engines mandated by Uncle Sam. You may not have that luxury in your country. But I can tell you it sucks here using that kind of fuel. These hypo motors do not like that stuff what so ever. Google piston soak techniques to do the piston. I have seen some and my engines get such a carbon buildup that it raise the compression ratio and start pinging from predetonation. This is also helped from crap fuel that wont burn. We use Sea Foam at 2-3 times the recommended rate on the can. The stuff works wonders on large displacement motorcycle engines and we buy it by the gallons. You need to put the bike in a holder to hold it in a strait up position and be able to put floor jack under the engine to raise it up and down in the frame. Be careful as you do this as there are water hoses and cables connected to the motor that can be broken. Also watch wiring harness that you do not want to pinch up or stretch out of shape. Also on my bike I remove the fuel pump to have better access to the top of the rear cylinder and remove the aftermarket air breathers under the tank. You will need to rotate the engine to get the cams in the lowest possession on the lobes to remove the pivot bolt/tube for the rocker arm assembly. When you pull this always use new O rings on the bolt/tube. Get a book and study the assembly. If you drop some thing in the upper rocker arm valley it can be fished out with a magnet and hemostats. There are springs and things that go on the shafts with the rocker arms. As you remove each item lay them out in order as you will need to replace later in the same order. The hydraulic lifter is on the end of the rocker arm on the valve stem end. Remove the lifter and replace and reassemble as you have laid out your parts. Watch for the springs on top of the oil filters when you first lift the vale covers. You can shoot these across the shop and look for them for hours. LOL Get a friend to assist you to hold them down when you reassemble the covers. Do not reuse any gaskets or you might find yourself with a leak. The older the engine is the more blow by it gets and these will leak.

02-04-2013, 06:11 AM
When I looked thru the manual I thought it should be possible but all info on the net was saying it has to come out but I think it should be ok.
Its like the vibration, all the people I have taken it to say it's normal- Im not an idiot-IT"S NOT NORMAL!
Anyway, we dont have Seafoam over here and I have tried a recommended alternative which did nothing.
When I got the bike it had only done 29,000 km's and the vibe started about a 1500 km's later.
Thanks for the detailed info, I will have to get into it soon.

Ken Means
02-12-2013, 11:29 PM
Cheveron Techron is the next best to Sea Foam. The same as Techron is Yamaha Ring Free sold at Yahama dealers. Don't know if you guys have Cheveron gas stations in the down under? For these Big Motors in bikes I still mix these at two to three times what the ratio calls for on the can.