Low power, dying when stopped
 

I have a 98 VTR 1000, and to admit I overfilled the oil at the beginning of the year, and had issues with the bike running rough until I figured the problem out. I corrected the oil issue, and things were running smoothly until about a month ago. It was dying at stop lights, starting hard, and surging at highway speeds. I changed the spark plugs, and the rear one was covered in oil. The front spark plug was fine, but I replaced both for good measure. After I installed the new spark plugs the bike started up fine, rev'd fine, and even seemed to have restored power. However, after about 10 minutes it was back to the old song and dance. Dying at intersection, low power, and burning oil, the only thing functioning normal is the idle. Once above 4500 RPM's it seems like I have normal power, but the low end power comes and goes. It seems like I am running a cylinder down at times, then the power pops in and the bike takes off. Additionally, when running at highway speeds 55 or greater I can feel an intermittent pull like it's calling for more power. Does anyone have a suggestion on where I should start next?

While burning oil is never good and can have a few different causes the rest of the issues listed sound like a major vacuum leak.

Fueling issues, start with a carb tear down and clean them meticulously. Do one at a time because they have different jets in the front and rear.
Have you removed the airbox lid and peeked inside after that oil overfill debacle?

Thanks for the suggestions. I haven't checked the airbox, in fact that I never thought about it. I suppose I will start taking the gas tank off to get to those pesky carbs, and I'll see if oil has flowed into the airbox at the same time.

Update: Carbs have been thoroughly cleaned. The air filter is clean, and no overflow of oil in the airbox. My rear spark plug keeps fouling out, and when I replace it the bike runs great for all of 10 - 15 minutes. then the rear cylinder seems to misfire, I have loads of power intermittently. The bike for the most part has stopped dying when stopped at intersections, but the power is unpredictable. Sometimes it will take off like a rocket, other times it is sluggish and accelerates at mule pace. Additionally, when I cold start it with the choke pulled out it doesn't want to start, but it seems to start fine with the choke pushed in regardless.

Is that a symptom a stuck or broken choke fitting on the back carb?

If you overfilled the oil in January, corrected the situation, and ran the bike regularly for several months without issue, then it seems you were past any potential ill effects of the overfill. How many miles between correcting the overfill problem, and when you started having issues?

I'm sure no expert but it sounds to me like you might have more than one issue. How long have you had the bike?

Alan

The Choke doesn't seem to be broken, It returns to a neural position on its own. The bike for whatever reason wasn't wanting to start with the choke pulled out which I just find odd because it never acted like that before. However, It is starting up just fine regardless.

I have ridden about 300 miles since the oil overflow incident, and all the oil has burned off and I don't seem to be burning oil anymore.

The symptoms of low power started when I overfilled the oil. Things ran great for about the first 250 miles, then it started smoking and guzzling gas.

The carbs have been thoroughly cleaned. I have checked the lines for rips or punctures, lines look good. I checked both spark plugs again. The front spark plug has no issues. This is the 3rd rear spark plug I've had to replace in 4 days though. The bike runs and sounds great when I change that rear spark plug, power is restored and I can do wheelies for days. Within half an hour the rear spark plug is shot and the rear cylinder stops functioning correctly ( I am guessing, I am far from a mechanic).

Another symptom I noticed over the week is now I seem to be getting awful fuel economy. I average 15mpg where I was averaging over 35 before. Could that be related to the rear cylinder not firing correctly?

Is it oil, or fuel fouling the plug?

Your presentation is confusing, at least to me. But I'm old. LOL. I recommend you focus on one symptom at a time. You need to sort this out a little in your own mind, else I fear you'll end up without any useful answers because it's really hard to pinpoint what your issue is the way it's being presented.

No one here is 'magic'. We need help from you to focus in on the issue.

Alan

Noted: I was throwing out the fuel economy issue in the event anyone has had a combination of these issues and happened to have a solution by chance. I see how throwing out a bunch of problems is counter productive.

The rear spark plug appears to be fouled due to oil.

The spark plug was saturated with oil the first time I changed it. The additional spark plugs have been damp but not covered.

To answer the smell of the oil. Yes, the oil has a smell of gas.

TerribleTerryTate, the fact that your rear plug is oil-fouled is troubling. You might not in fact have escaped the ill-effect of over-filling the engine oil. Maybe you know the potential effects, e.g., aeration. Your engine might have suffered some internal damage due to the effects of excess oil. Don't take the following too seriously. I'm not a mechanic...

As for the oil-fouled plug, and your description of how the engine runs, these are consistent with my limited experience of an engine with an oil-fouled plug. At lower RPMs it misses like a son-of-a-gun; at higher RPMs, e.g., if you really get 'on' it, it will smooth out for a bit. In between these two states, it's kind of random as to missing/running smooth.

I would start thinking about pulling the engine down, inspecting the head (guide seals) and the cylinders/rings and associated tolerances. Hopefully one of the folks on here with a good amount of expertise will chime in. But that's what I'd be considering, at this point. Sorry, I know you want to hear better news. If the oil was aerated, and didn't lube the cylinders, the rings could wear real quick (or even chip/break) and subsequently you'd have a lot of gas passing by the rings into the pan...and REALLY gassy-smelling oil. (The Oil smells a little gassy on all my bikes; but if it's a really STRONG smell, that's probably a clue there's something out of the ordinary going on).

Out of curiosity, how many miles did you ride before you caught the overfill?

Alan

I rode the bike for 50 - 100 miles before I started experiencing issues with it running rough, and starting trying to source the issue. The oil has a pretty severe smell of gas. I was thinking I might have a bad seal or O ring in my rear cylinder. I have been considering taking the bike in and having them run a compression test, but I am unsure whether this is beneficial to helping narrow the issue down.

If I were you I'd do a compression and/or leak down test to determine if there's an issue with valves, rings/cylinders. Again, I'm not a mechanic. But your symptoms--oil-fouled plug, missing--indicate something is amiss. One or both of these tests can direct you toward the next diagnostic procedure. If they indicate the compression is good, then it kind of rules out rings, valves, etc., and you can focus on other things. They shouldn't charge much for either test, maybe 1/2 hour to 1 hour shop time. Out here in Cali that'd be about 50 - 100 bucks.

Alan

Where is the bike at? Maybe someone on here could help you out if they are close.

I'm in Iowa

I have not read the entire post but a compression test and leak down test seams to be in order. before you take the engine apart.
also I would take the airbox lid off and hang a clear gas container hook it up to the carbs run seafoam through the engine to clean the top end and then mark the clear gas container level and see if leaks down at all. you will have to rev it to keep it running.
The reason I would clean the top end is maybe you have a lot of carbon built up from running it with the oil overfilled. Do the compression and leak down test before and after you run the seafoam. did you sync the carbs and check tps adjustment. as you said that you had taken them apart.

@Stumpy,

The carbs have been synced, and tps adjusted at .800. That's all I know, I had a buddy who is much more knowledgable help me with the carbs.

How much did you "overfill" the oil and how long and hard did you run it before you corrected it?

I emptied a total of 6.5 Liters of oil in the bike once the overfill was discovered. My bike usually likes 3.75 Liters, I am not sure what I was doing when I put so much oil in it.. anyway. The bike ran for 50 - 100 miles before I noticed it running rough and smoking and decided to investigate.

I had similar issues with power problems and it turned out to be the rectifier ( RR ) and I replaced it and it was fine after that... If your spark plugs were covered in oil, if the oil was baked on it may be preventing a strong spark so replacing them can't hurt, but you can check the spark first to see if it looks weak - you already replaced them and it was better for a short period of time and then was bad again - so it could be a blown oil seal somewhere.... How new is the battery? Rough starts aren't uncommon when a lot of fuel is being pumped it before a spark is strong enough to hit it so it could be power related - but it could be an oil seal or something pumping too much oil or mixing with the fuel meaning larger particles when sprayed into the cylinder meaning less 'fumes' so less likely to start properly....

All in all, it could be a combination - if you've never replaced the rectifier regulator or whatever it is called, it is basically the alternator - a good test would be to attach probes to the vehicle and check voltage readouts as you drive and experience the issues....
But you've said you're back to burning oil - so too much oil is likely entering the fuel system or is actually mating with the fuel...

It could be something completely different - I don't recommend spending money until the problem has been diagnosed fully...

@acecool,

Thanks for the info. The battery is a couple months old, and I have kept it maintained / charged. The last time I changed the spark plug the rear cylinder spark plug wire looked corroded so I just installed a new one, and replaced the rear spark plug again. At this time I drained the oil again and replaced everything fresh. it took 3.75 quarts with a filter change. Everything fired up and sounded great for about 5 minutes. then I had a loud backfire and it started smoking severely. I let it run for about 15 minutes and the smoke went from dark to a light grey. The idle is smooth but a little lower than expected, maintaining around 600 rpms. Additionally the strong gas odor from the oil seems to have resolved itself with the most recent oil change. I have a compression and leak down test scheduled for later this week. I am hoping it is something as simple as a blown gasket. I will take the regulator suggestion into consideration next.

600rpm is way too low!
1200rpm is the goal

Just finished the compression test on the rear cylinder. The rear cylinder is producing 100 lbs of pressure at idle, and 190 at 4,500 rpms or greater, which is most likely the cause of the low idle. At this point, I don't think there is anything more I can do aside from having the motor stripped to find the cause for the low compression.

Thanks for all the input guys.

How do you perform a compression test at 4500 rpm's?

Or for that matter, at idle? Throttle butterfly would limit air intake - no?

youre saying you screwed in the idle speed adjustment knob as far as it will go and you're only getting to 600 rpm?