Power loss on '88VR...

[yamadawg]

Entering Missouri and just after getting fuel on the way back to East Tennessee from Sturgis my '88 VR I experienced a noticeable loss of power and more noise coming from the engine, almost as it there were an exhaust leak at one of the front cylinders. I thought it was bad gas and would get better with the next tank. With the next fill up I added HEET gas treatment to dissipate any water that may have been in the fuel, but with no noticeable improvement. We were pulling a trailer and riding two up. The bike has a loss of power and takes much longer to get up to speed, but cruises fine at 75 - 80 mph. The bike sounds much louder from the drivers seat upon starting off from a stop and the problem feels as if the engine is "bogging down". The loss of power is noticed more upon moving from a dead stop or upon encountering a steep grade. However, it does start and idle fine. Where would be the best place to start to diagnose and remedy this problem? Up until this time the bike had ran great with excellent power, and it has only 59,500 miles on the clock...

 

Thanks!

Don

[GeorgeS]

Well, based on many stories of common problems:

 

Possible bad connection on one of the plug wires.

Remove each plug cap one at a time and check for RPM drop at idle speed.

If so, check plug wire on the plug cap for that cylinder,

and replace that plug.

 

Possibly one of the Ignition coils is going bad.

 

Run 1/2 can of Sea-Foam per tank for a couple of tanks.

 

You might Drain all 4 carb bowls, might be foriegn matter in one of

the bowls.

 

Check the overflow hoses, from each carb, that run down behind the muffler crossover canister. One of them might be plugged with road debrie, I have heard of this happening. This will block air bleed to that carb

 

Possible bad or dirty , corroded, connections on the Two Plugs that plug into the TCI.

 

Possible, high resistance across the 40 Amp Main fuse, or across the ON-OFF contacts in the Ignition Switch, get some contact cleaner at radio shack, spray can, and give the switch a bath, and blow out with compressed air. (( If high resistance at any of these two points, it will lower the voltage to the Ignition Coil Primary windings ))

[bongobobny]

GeorgeS has given you some good advice. I personally am thinking contaminated carbs based on when the problem started but it could be coincidental to another failure. You may want to pull your airbox cover and observe whether your sliders are working or not. You may have developed a pinhole in one of your diaphrams...

 

Also, with airbox cover and filter out, it's a good time to spray a can of carb cleaner down the throats.

[Leadwolf56]

Everything they said above and also check your fuel filter. Mine clogged up a week above. Mine clogged up a week after we got back from Colorado. Looked like the ethanol in the gas we bought out west cleaned stuff out of my tank.

[Gearhead]

"You may want to pull your airbox cover and observe whether your sliders are working or not. You may have developed a pinhole in one of your diaphrams..."

 

 

 

You won't detect a pinhole by watching the slides dance. 3 out of 4 of mine were seriously cracked through, much more than a pinhole, yet the slides all appeared to dance about the same as far as I could tell by looking. Remove a carb top cover and take a slide out to look at the diaphragm instead - not very hard to do.

 

Jeremy

[matt73ander]

i would check the fuel filter for sure, I know that swwitching changing to higher and lower ethonal levels tends to make the filters more likley to clog.

[Condor]

Betcha money, marbles, or chalk you've dropped a cylinder. These V4's will run good on 3 cylinders. It just feels weak but will still cruise along at highway speeds. Change out the plugs and see if that doesn't help the situation.

[Black Owl]

I'm with Condor on this one. I would bet you have a bad plug in one of the cylinders......

[yamadawg]

After changing plugs and checking the electrical ideas, then changing the fuel filter to no avail, I have found the problem. The nozzle for the main jet in the front left carb has came loose and slid out of the housing onto the needle. It looks as if this cylinder has probably been running way off... I took of the side cover, pulled the diaphram and pulled the nozzle right out. It appears to be keyed to fit in fully only one way. When this is seated in the bike runs great!

Now for my question... Can I carefully Super Glue this in to prevent it from working back out again? It looks like the back of the nozzle is threaded but I cannot tell if there is a way to get to the other end to determine if a screw is there. Plus, if I pull the carbs I am sure to screw up even more stuff.

[Cutty]

That is called the emulsion tube, your main jet screws in the bottom of it. So pull the bowl and put the tube back in and make sure the main jet is tight.

[hipshot]

Betcha money, marbles, or chalk you've dropped a cylinder. These V4's will run good on 3 cylinders. It just feels weak but will still cruise along at highway speeds. Change out the plugs and see if that doesn't help the situation.

damn jack! you're tellin' your age , now!

i haven't heard "money, marbles, or chalk", mentioned in the same sentence, in MANY years!

lol

 

just jt

[Condor]

damn jack! you're tellin' your age , now!

i haven't heard "money, marbles, or chalk", mentioned in the same sentence, in MANY years!

lol

 

just jt

 

 

LOL... yeah, it's an old age thing....

[Gearhead]

"That is called the emulsion tube, your main jet screws in the bottom of it. So pull the bowl and put the tube back in and make sure the main jet is tight."

 

 

 

Yup Yup Yup. That's whatcha gotta do. The emulsion tube is sometimes called a needle jet, and you have to pull the carbs to get the bowl off, where presumably your main jet is rattling around.

 

Jeremy

[yamadawg]

The correct answer was:

"That is called the emulsion tube, your main jet screws in the bottom of it. So pull the bowl and put the tube back in and make sure the main jet is tight."

 

BUT... then it should have said "Don, you dummy. Tight, but DO NOT OVERTIGHTEN. This screw is made of brass, is hollow, and will snap like a twig. Then you will have to wait for days to get this back together.:no-no-no:"

 

Boy, I sure like riding 'em a lot more than working on 'em.

 

Plus, now I will be scared to use a screwdriver...

 

Having a ball, wish you were here,

Don

[Guest Popeye]

damn jack! you're tellin' your age , now!

i haven't heard "money, marbles, or chalk", mentioned in the same sentence, in MANY years!

lol

 

just jt

 

I've never heard that. Therefore, I must be a youngster.

 

I had a similar problem last May, but it was rust from the tank & carbs had to be redone, sliders, diaphragms, acid-wash & reline tank, and everything else we do just because the thing is already taken apart.

 

I'm buying a New Bike.....one part at a time.

[yamadawg]

Here's a big thank you to all of the folks that responded and especially to mbrood who helped walk me through fixing this problem and to Rick H who provided advice, great pricing as usual, and expedited the parts to me. With this guidance I test rode my bike tonight and will be smiling for days. It is back to full power and pulls the front wheel up in the first three gears. (At that point I have exceeded the maximum safe allowable speed:no-no-no:, so who knows about fourth gear:whistling:.)

What I learned beside the fact one of the prior owners did a poor repair job was that my problem has been somewhat progressive. I had noticed a small loss of power and occasionally felt the performance was missing slightly, or just not quite right. With the emulsion tube now firmly attached the bike now has remarkable power and instant throttle response. It seems much more like I remember my old '83 to have been... the '83 always seemed to be a little quicker.

Thanks again to all and happy riding!