Low-mid RPM loss of power


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johnWK
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Low-mid RPM loss of power

Post by johnWK » Fri Jul 27, 2018 2:13 am



Very recently I was riding to work, nothing amiss. As I rounded the corner onto a long straightaway I cranked the throttle back, the bike jumped to life, shifted up into 2nd gear and as it was about to really take off I lost almost all power and acceleration. The bike was still running, but again little to no acceleration after roughly 4-5k. At first it was just an issue in 2nd gear and above, but earlier today I took her out quick and she started dying and losing power in 1st gear too.

I'd noticed recently that my fuel pump was spurting gas out of the weep hole at a fairly decent clip. I'm thinking this issue may be related, but before I go pulling her apart I figured I'd check with the experts and ask where I should start looking first. New fuel pump? Carb rebuild? I haven't heard any vacuum sounds upon opening my gas cap that I can recall but I'm already looking at replacing the original just to rule that out.


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DaveO430
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Re: Low-mid RPM loss of power

Post by DaveO430 » Fri Jul 27, 2018 5:34 am

No, it couldn't be the leaky fuel pump, must be a missing tail light screw or bad blinker fluid or something.

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DenverWinger
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Re: Low-mid RPM loss of power

Post by DenverWinger » Fri Jul 27, 2018 9:16 am

Sounds like the Knuter Valve is stuck. You can check it with a two-way Plebney Light.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

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johnWK
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Re: Low-mid RPM loss of power

Post by johnWK » Fri Jul 27, 2018 10:44 am

Hardy har har. Would this be a good time to mention I am a very inexperienced home mechanic? Because I'll be the first to admit it, I am. I'm glad yall are having your fun, but any actual advice would also be appreciated. Judging by the first response, it is indeed a fuel supply issue. I'll start there.
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DenverWinger
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Re: Low-mid RPM loss of power

Post by DenverWinger » Fri Jul 27, 2018 12:12 pm

Sorry, nothing bad intended by the replies :)

Here's a DIY article for replacing fuel pump, if you have gas coming out the weep hole it is likely a bad diaphragm. viewtopic.php?f=11&t=161 If you scroll further down in the posts there's pictures showing the pump taken apart, the DIY simply covers replacing the entire pump, but might be able to order just a diaphragm. Guru's, any sources for just a diaphragm?
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark

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johnWK
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Re: Low-mid RPM loss of power

Post by johnWK » Sun Jul 29, 2018 12:02 am

Did a some more looking on the site for similar issues and it would seem the failing fuel pump is most likely the cause of my power loss. Just ordered an OEM replacement. Replacing the diaphragm looks to be a more complicated task that I'd rather just avoid, and don't own the tools to accomplish.

Thanks again for the help ;) I'm sure I'll be back with another dumb question soon.
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Re: Low-mid RPM loss of power

Post by Wingsconsin » Mon Jul 30, 2018 4:10 pm

johnWK wrote:
Sun Jul 29, 2018 12:02 am

Thanks again for the help ;) I'm sure I'll be back with another dumb question soon.
The only dumb question is the one you didn't ask...
Don't let the curmudgeons here scare you off --
-- in reality most of them would come over and help you turn wrenches if they were close enough
Keep asking - keep learning - keep riding - :ugeek:

Postings are my opinions based on experience and acquired knowledge.
Your results may vary. Universal disclaimers apply.


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http://neverlost-justexploring.blogspot.com/

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johnWK
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Re: Low-mid RPM loss of power

Post by johnWK » Sat Aug 11, 2018 9:22 pm

Got the new pump on there and the bike was riding like new, not a leaky weep hole in sight and pulling up to the redline as fast as I could roll on the throttle.

Until this morning. Took her out, taking it easy until she got warmed up, and then started putting her through the paces. Got up into 4th gear and was about to the redline when I felt the acceleration and speed give out. Acceleration in gears 1 and 2 is less snappy, and in 3 and 4 when I lay on the throttle a little acceleration is very noticeably weak and will not climb up to the redline. I can hear the engine revving up as I watch the RPM's quit climbing, making me think I might need to reseat the tach. The engine stumbles barely when I roll on the throttle on the higher end of 3rd gear. I can still reach and maintain highway speeds, but not nearly as fast as I know she's capable of. Fuel filter looks clean, fresh pump, no leaks so far. Put fresh plugs in today and charged the battery just to see if it would make a difference, and it didn't. Was running fine this morning until I felt it give out during some hard acceleration.

Any ideas where I should start looking for issues first? I just ordered new lines, a filter, and clamps as per the recommendations on WingAdmins line replacement DIY. Been looking around a bit and I'm now wondering if it's time to check my 36 year old coils, which I'm not entirely sure how to do. While on the topic, how would one check the health of their plug wires?
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DenverWinger
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Re: Low-mid RPM loss of power

Post by DenverWinger » Sun Aug 12, 2018 7:56 am

Checking coils sounds like a good place to start, one coil fires the front two cylinders, the other the rears. With engine idling pull off a sparkplug wire. If a coil is bad and you pull a wire on the good coil the engine will probably stall, if you pull a wire on a bad coil little or nothing will happen. Ideally on a good running engine you can pull a sparkplug wire, the RPMs will drop some but it will keep running.

A good coil should be able to jump a spark a half-inch, you'll hear it snapping...

As to the wires, they are solid core so there really isn't anything that goes wrong with the wires, but the insulation can start to give up, most noticeable in the rain or damp weather. You can check that with a spray bottle of water to see if there's any sparking around the outside of the wires somewhere or the engine begins to miss.

I think the 1100 has resistors in the sparkplug caps. With an ohmmeter you can check the coil and sparkplug resistors by measuring ohms between one sparkplug cap to the opposite one, should be on the order of 15-30K ohms IIRC. If significantly higher than that likely a bad coil or sparkplug resistor. If the reading is questionable Sparkplug caps detach from the wires, that way you can measure the coil directly. Resistors in sparkplug caps are 5K ohms each IIRC. At one point my 1100 would start missing if it was damp out, the caps had degraded and sparks were snapping from the sparkplug caps to the cylinder head inside the sparkplug recess. I replaced all four, problem solved. If you find bad sparkplug resistors, I wouldn't bother with the resistors, just get new caps.

That should get you started, post results. And BTW, did you ever get that blinker fluid changed? :lol:
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark

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johnWK
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Re: Low-mid RPM loss of power

Post by johnWK » Sun Aug 12, 2018 11:37 am

Got the blinker fluid changed alright, DenverWinger. Set the rest of the can right next to my strawberry de-seeder.

Just went out and pulled the plug wires as you suggested, and as you said the engine would drop in RPM each time but the bike never stalled out. I could hear the plugs snapping in their recesses. I'll check with an ohm meter, think my dad has one in the garage, and see if anythings off. The PO didn't mention replacing them as far as I can recall, but it looks like the plug wires/boot are newer than original so I'm kind of thinking my problem lies elsewhere. Any other ideas where to look next? Compression? As I said, I'll be replacing the fuel line and filter hopefully by mid week.
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johnWK
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Re: Low-mid RPM loss of power

Post by johnWK » Sun Aug 12, 2018 1:39 pm

Man, are you guys going to love this. Queue up your blinker fluid and Plebney valve jokes. There was indeed a sudden, noticeable loss of power and acceleration. I found the cause of it about 30 minutes ago. My darling is now screaming up to the redline and far surpassing advisable speeds. Engine idles like a sewing machine. I "fixed" the issue...or rather removed it :lol:

Damn. Should've known my otherwise perfectly functioning GW was being crippled by my own oversight. To quote myself, "Turns out I'M the idiot."

Anyone want to guess what the issue was?
memento mori

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Re: Low-mid RPM loss of power

Post by Maz » Sun Aug 12, 2018 3:13 pm

Please don't say the choke was on!
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Ironically, Common Sense is the LEAST common of all senses!

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johnWK
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Re: Low-mid RPM loss of power

Post by johnWK » Sun Aug 12, 2018 5:03 pm

Nope, but almost just as obvious. Left a polishing rag on top of the air filter box, both ends of it plugged up the intake windows.

Thanks again for all the help and advice.
memento mori

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Re: Low-mid RPM loss of power

Post by Earl43P » Sun Aug 12, 2018 6:31 pm

We ALWAYS appreciate knowing the final fix. In your case I was one of my personal favorites, the FREE kind. Good work!
When all else fails, RTFM!

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Re: Low-mid RPM loss of power

Post by Maz » Mon Aug 13, 2018 1:45 am

johnWK wrote:
Sun Aug 12, 2018 5:03 pm
Nope, but almost just as obvious. Left a polishing rag on top of the air filter box, both ends of it plugged up the intake windows.

Thanks again for all the help and advice.
You see.....there are advantages to not cleaning your bike! :lol:
Maz
Ironically, Common Sense is the LEAST common of all senses!

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Re: Low-mid RPM loss of power

Post by Hoosier Jack » Mon Aug 13, 2018 6:09 am

Self inflicted wounds breed future success. I live by that rule. Apparently.



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