Engine losing power

[Hughie]

Hi there I was out on my voyager xii last night. It was riding great up until the point I started to loose power and the engine was shaking. I was quite concerned that I wasn't going to make it home!I

I did make it home but the voyager was certainly limping all the way.

The engine is running ok at low speeds on the flat, it's when I open the throttle the engine is unhappy looses power and starts shaking, more noticeable on inclines. I have put the bike in neutral revved it up and running fine. I also put a can of sea foam through bike about 500km ago prior to this problem. It will get up to 120kmh on the highway and cruise there ok providing no hills. It seems to have problem more on the hills when I am asking for more power.

I bought the xii 4 years ago and put 41k on it and never had this problem before. Any assistance would be greatly appreciated.

Hughie

[bikerking.biz]

Think the first thing I would check it the front of the driveshaft to see if your U-Joint has play in it. That could be the shaking or vibration that you might be feeling. It would probably reduce power some too.

[Mr Jensee]

Also it could be due to the fuel filter being clogged or the fuel pump having issues.

[cushman eagle]

Also it could be due to the fuel filter being clogged or the fuel pump having issues.

I agree,Mr.Jensee,it sounds like a fuel starvation problem!

[Hughie]

Thanks for the ideas gentleman, I have ordered a fuel filter, it will be here next week. And I will check the U bolt when I have found it! Update to follow.
Hughie

[jengstrom]

When was the last time it was tuned up? If the low power and shaking is due to engine missing, fouled and/or worn out plugs are a classic cause. A new fuel filter and air filter can help too.

John

[Hughie]

The last tune up was 40k ago. It had new plugs at that time I believe. I will order new plugs. I have already ordered fuel filter and air filter.
Thanks for the info
Hughie

[cranky]

I put iridium plugs in mine and it made a noticeable difference!!!! JM2C

[Hughie]

Thanks for the advice Cranky, i have ordered the iridium spark plugs today .
Hughie

[Hughie]

Hi everyone
Thanks for the advice, I put new iridium plugs in, new fuel filter, new air filter and unfortunately I am still having the same issues.
Just a re cap then on what is happening.
Starting fine.
Ticks over at idle ok
Engine running ok below 3000rpm
The problem starts when I try and accelerate over 3000rpm, i loose power and the engine gets bogged down, when I ease off the throttle the engine runs ok. I can get the bike up to 70mph and still running ok as long as I accelerate slowly.
Thanks for helping out
Hughie

[SgtSlag]

Based on the fact that it idles normally, but loses power when you are opening the throttle, it seems as though the main jets, in the carburetors, are the issue. The smaller jets feed the engine until you reach the upper RPM's, or you open the throttle for power; that is when the main jets open up, and pour larger amounts of fuel into the engine. Without proper troubleshooting, it is just an educated guess.

At this point, you have thrown parts at it, and you have achieved very little (you've actually purchased insurance to keep key components working well into the next 50,000 Km -- all good, will pay out in the long run). If you are at the end of your rope, it may be time to take it to a professional whom you trust. I hate to see you throw more money and parts at it, hoping to get lucky. Cheers!

[Nails]

This can give you a rough idea: try rapping it up until it bogs, let it flail like that a few seconds, and then hit the kill switch (keep the throttle where it was bogging). Then look at the plugs, especially for gobs of carbon.

[Hughie]

Thanks for the ideas
Just a bit more info. The engine will rev greater than 3000rpm normally in neutral.
The problem occurs when in gear riding down the road.

[doug of so fla]

When it looses power under load it could be you have a spark leak or bad coil. Spark leak could be at plug cap (very common on XII), also plug wires, check for corrosion at wire going into plug cap. Quick check for spark leak is; in a dark garage cover or disable all lights and start XII and look for blue light arcing somewhere along the ignition wire paths. Even though it is not under load you should see a blue spark leak.

[Nails]

> I put new iridium plugs in

What did the old ones look like?

> sounds like a fuel starvation problem

These Keihin carbs are also sensitive to the fuel level, which can and does bump out of spec. There are other threads here about testing that without removing the carbs by attaching a clear line to the float bowl drain and holding it up to indicate the fuel level in the bowl. It's a PITA, but not as much of a PITA as removing the carbs. And this method may be more accurate than measuring the float height. (Some do this check on the bench.)

If you want to check it, I'd recommend installing a switch to defeat the starter relay. That'll be a lot easier on your battery, when you need to refill the float bowls to check them. See other threads about that switch (recommended for other reasons as well).

I've seen floats get stuck, in one case from gasket sealant that bulged into the float bowl -- probably why you aren't supposed to use gasket seal here. In that case, it was an intermittent misfire that occasionally occurred on hard uphills. (I think this is a very rare problem.) But my point is that you might have to pull the carbs anyway to inspect the float bowls &etc. I only figured that one out by looking in the float bowls.

Assuming that once upon a time the float heights were right, I would only suspect the fuel level if it's just one cylinder, which you can figure out by looking at the plugs as mentioned above. Since it occurs under load, that plug probably would be lean. A bad coil would affect two cylinders, and those plugs would show rich. A spark plug leak might not show on the plug color at all -- but sometimes you can see spark tracks on the ceramic insulation. Besides the light show Doug mentioned, checking the plugs might be the least PITA of all, even if you're doing it on the side of the road. It won't fix anything, but it might save you a world of Ewak even just figuring out whether it's spark or carb.

[Hughie]

Hi everyone
Thanks for all the ideas.
I have been riding around on the xii for this last week hoping the bike would fix its self. I was in my 3rd tank with sea foam added thinking if it doesn't start running better on this tank I will take it to the shop. And fortunately the bike has now fixed its self. Running normally. Actually better than before, likely because of the new spark plugs. I am hoping the problem will not return. At this point I'm putting it down to dirt in the carburettors. When the problem occurred i only had perhaps 2 litres of fuel in the tank and could have got some dirt from the bottom of tank maybe.
Thanks Hughie

[triton28]

I'm glad it worked out for you. I always drain the float bowls at least twice a year to avoid any chance of crud buildup and when I lay the bike up for winter I drain them again. Some don't bother to drain the bowls but for me I always do. With a long #2 Philips screwdriver/allen wrench it is such a simple operation I find it is worth it. YMMV.
Dave

[Mr Jensee]

Hughie now you see why you need to have plenty of gas in the tank. trash in the bottom will definitely mess with the fuel flow. Glad you have it fixed my friend. Your trial and error plan worked.