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Old 10-22-2013, 01:16 AM   #1
batoutoflahonda OP
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R80 lost top end speed. Head scratcher.

Within the past week or so, my '81 R80G/S has lost it's top end speed. On a flat run it will hit 90 at 6K RPM, but that's it. Coming over my mountain pass
commute, best it will make is 80. It will hit red through 3rd gear, and the tach needle looks like the tach is "clipping" under acceleration (gets it's input from the coil), but just for a bit. Every where else the bike runs like a clock. No ping, knock, or oil consumption. Plugs are a nice tan. Fuel consumption is up, but I think it's because I am screwing with it. It pulls all the other hills fine and it used to pull the pass at 90+ (it's a nail biter on the WA freeways close to 100, so never got it past 101. The roads here have gone to crap since the shutdown.)

It has been converted to points with a dyna booster.

Been through the carbs, clean. Changed the diaphragms, no help.
Points are set. Carbs balanced.
Top ends/pistons done two years ago and valves are adjusted properly.
New spark plugs and the wires are good.
Fuel flow is around 400cc/min./side.

Really it acts like it just isn't getting enough gas, or has a major vacuum leak. The carb boots look good. Can't find any thing wrong with the fuel system.

So, I'm going to change the condenser thinking that my be causing the tach to clip, and maybe be my problem. If that doesn't help, pull the tank and ohm out the coil. I haven't done a compression check yet.

Am I headed in the right direction thinking it's electrical? Or is there some thing I'm missing? Any one have this problem?
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batoutoflahonda screwed with this post 10-22-2013 at 01:32 AM
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Old 10-22-2013, 02:01 AM   #2
ME 109
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Open the throttle fully and see if you can pull/push on the cables just before they connect to the carbs.
This will prove whether or not your cables/throttle handpiece are in order and fully opening the butterfly.
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Old 10-22-2013, 02:17 AM   #3
Plaka
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Quote:
Originally Posted by ME 109 View Post
Open the throttle fully and see if you can pull/push on the cables just before they connect to the carbs.
This will prove whether or not your cables/throttle handpiece are in order and fully opening the butterfly.
yeah..you can also just reach down doing 80 at WFO and haul on one of the throttle cable housings and see if there some more there you aren't getting.

I would check timing and clutch adjustment. Especially check point gap. it is theoretically possible to run out of dwell at high RPM, but unlikely. If the booster uses a condenser (confirm it) then change that and clean it's grounding point.

Look for loose connections at the coil low side, clean the spark plug cables both ends and the coil sockets, silicone lube in both.

Test the coil for good sparks leaving the plugs installed and putting a brand spanking new plug on the cable end, and grounding it.


Slow the fuck down. Getting killed is your business. Not leaving enough of a wreck for someone else to build back up is every bodies business.
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Old 10-22-2013, 02:49 AM   #4
ME 109
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Originally Posted by Plaka View Post
yeah..you can also just reach down doing 80 at WFO and haul on one of the throttle cable housings and see if there some more there you aren't getting.
Well I did start typing 'reach down with your left hand and'...................but then I also thought about batoutoflahonda not leaving enough parts for us.

As it is pulling redline in third, I would first suspect yo butterflies not fully opening.
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Old 10-22-2013, 04:18 AM   #5
JonnyCash
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You could have a pinhole in one of your diaphragms, your timing may be off, float levels low causing lean condition, tank vent blockage causing lean condition. Check your coil wires. I had a similar thing on my RD and I found the coil wires were corroded where the wires went into the coil. It ran great except at the top of the rev range under WOT. Even then it wasn't bucking like you'd expect, it would just surge a little, and not make the kind of power it should.
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Old 10-22-2013, 04:48 AM   #6
Stan_R80/7
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The dyna booster I used did not require a condenser - but the condenser could be left connected to the points. The points act as a digital switch for the dyna booster (DC voltage) and the condenser is there for converting back to standard points use (when the dyna booster fails).

I would check the float bowl levels and the ignition timing. I would also consider running a can of fuel system cleaner through the engine - for no other reason than it will help clean carbon off the valves. If the ignition system works fine in third gear at 7k rpm, no more electrical energy is needed to operate in fifth gear at 7k. But, being thorough and meticulous in checking the coils can't hurt. Good luck!
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Old 10-23-2013, 06:41 AM   #7
Uncle Pollo
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Quote:
Originally Posted by ME 109 View Post
Well I did start typing 'reach down with your left hand and'...................but then I also thought about batoutoflahonda not leaving enough parts for us.

As it is pulling redline in third, I would first suspect yo butterflies not fully opening.
this
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Old 10-22-2013, 02:58 PM   #8
disston
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You have a bike with ignition points. Therefor the first thing to check for most performance complaints is the ignition dwell and timing. This particular complaint is often a small hole in diaphragm tho.

If points are right and diaphragms are right there may still be an ignition problem. I don't ever see may other riders report this but when a Dyna Booster went out on my bike almost ten years ago it got weaker and weaker in a couple of stages. It did not die all together at one time. I got some miles with poorer performance before it was completely dead. Then when I went back to stock points the bike was fine again. So if everything else looks and tests fine revert ignition back to points only to test if there is a problem with the Booster.
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Old 10-23-2013, 12:51 AM   #9
batoutoflahonda OP
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A friend suggested winter gas. I dismissed it as witchcraft. Then I pondered some octane boost. Then I thought about getting a shaman and some herbs. So I settled on Seafoam as I thought maybe there was water in the gas. Seemed to cover all my bases, according to the lable. I needed spark plugs any way.

So checked the timing and all is good. It does hit the throttle stops and I have tried shifting into lower gears, but still can't get it to red line on the pass. Climbing the Snoqualmie pass, if I down shift it struggles to get back up to the speed it lost on the down shift. In a flat run I can get 7k rpm in the first three gears. 4th and 5th it won't get much over 6k @ 94 mph, fastest I could get it today. The point gap is good. I wondered about the dyna and the condenser, left it hooked up so I could switch on the road if need be.

I stuck new diaphragms in the other night, before this post. Didn't see any holes in the old ones, but wondered if they might be weak. It actually helped with the response a bit. I do notice just a very slight hesitation rolling on at part throttle. The new diaphragms actually helped with that, as it was noticeable before. Now I can feel it, but ever so slightly.

Thinking I'm going to get a new set of points and condenser on order. Check the coil. One thing I have also been pondering, is the Y collector for the exhaust rattles when I start it. This started a while ago. If I kick it, it stops rattling. Thought it was kinda amusing, but wondering if a baffle hasn't come loose and is plugging it a bit. Sucks, because all the new ones are shiny. It will just totally clash with the patina of the bike. Suppose I should bite the bullet and check compression. Would be a total bummer if it went south after two years and maybe 20k miles.

Thanks for the replies so far. And the English lesson. This bike is so cool in that runs no matter what, and through this whole thing the past few days, every thing I tweak here and there helps it run better. Probably the best I've ever tuned it. That's what has me so perplexed. Even when it's acting up, it's fun to try diagnose. It's an amazing piece of machinery.
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batoutoflahonda screwed with this post 10-23-2013 at 01:17 AM
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Old 10-23-2013, 01:24 AM   #10
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Main jet too rich? The weather is gettin colder. The term pass makes me think high elevation. Winter gas.

Add to the above your bike should have no problem breaking 100mph.

Kinda surprised supershaft didnt offer this first.
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Old 10-23-2013, 04:31 AM   #11
Stan_R80/7
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Sounds like it's time to check the engine compression. My low compression R80/7 shows 150 psi on each cylinder. Good luck!
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Old 10-23-2013, 06:40 AM   #12
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Quote:
Originally Posted by SprintSix View Post
Main jet too rich? The weather is gettin colder. The term pass makes me think high elevation. Winter gas.

Add to the above your bike should have no problem breaking 100mph.

Kinda surprised supershaft didnt offer this first.
Cold weather would ask that you richen the mixture actually. Air is denser at lower temps, more oxygen in the intake means you want more fuel.
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Old 10-22-2013, 07:01 PM   #13
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When my airhead failed to get pass 5K rpm, it was because of a broken ring in one of the cylinders.

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Old 10-22-2013, 07:16 PM   #14
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I'd CAREfully check the diaphragms. Sometimes you need to gently stretch them a bit and hold them up to the light to see smaller tears in them. It doesn't take much of a hole to make a big drop in power.
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Old 10-22-2013, 07:21 PM   #15
Plaka
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Originally Posted by Airhead Wrangler View Post
I'd CAREfully check the diaphragms. Sometimes you need to gently stretch them a bit and hold them up to the light to see smaller tears in them. It doesn't take much of a hole to make a big drop in power.
it also takes little stretching and poking to turn a perfectly good diaphragm into junk. At which point you get to replace it, think you found the problem and find out you haven't.

If it is running lean at high RPM due to a diaphragm problem, it won't be on both sides. So a look at the plugs or quickly check head temps with a cheap IR thermometer to reveal the condition. Then you go looking for a cause. If you find no evidence of it running lean, go looking for something else.

OP stated plugs were normal. But he didn't state if he did a high speed chop when the power was down.
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