Power loss
Harley EngineDiscuss Power loss in the Harley Tech & Harley How-to forums; My 96 EVO has developed a power loss problem that has me baffled. The problem started out intermittently and is now constant. The power loss occurs throughout the throttle range ...
My 96 EVO has developed a power loss problem that has me baffled. The problem started out intermittently and is now constant. The power loss occurs throughout the throttle range and is accompanied by more than normal vibration. The exhaust note also resembles a single cylinder machine(Buell Blast, Suzuki Savage). My fuel economy also suffers from a loss of about 20 miles per tank. The bike is stock except for a new exhaust system, carburetor(Mik HSR42),and air cleaner. All mods were done last year and have been working fine thanks to many members advice(Especially Frisco). The only other change was a tune up that also occured last year. I did try another set of plugs. The old ones showed a slightly rich condition. The problem seems less during warm up but quickly returns. The bike is ridden just about every day rain or shine. Any suggestions are greatly appreciated. Thanks!
Um, are you absolutely sure it is NOT running on just one cylinder.?
More than normal vibration, power loss, mileage gone to heck----- and sounds like it too, well, it could be..
Have you tried to see which cylinder might be having the trouble.?
It sounds like spark//electric to me..
Sometimes when an elect. connection, like at the coil or one of the plug wires, is just barely making contact, it will be Intermittant at first but then lose contact..
I would check all connections that are spark related first.. Your ignition connections, spark plug wires at the coil and plugs, and even look inside the plug-wire boots, where the spark plug connector and the coil connection that slips inside the coil, are crimped onto the wire.. Get out the meter and check plug-wire continuity.. And don't forget the ignition switch wires..
And while you're at it check the coil.. Dis-connect all wires from the coil then check OHM's in both circuits--primary and secondary.. It explains in the book if you don't know already.. Start eliminating baby..!
What ignition are you running.?
This has happened to me a few times.. It was the single-fire electronic ignitions going bad.. Hopefully it's not that with you..
When either the rear or front modual dies you are left with just one cylinder..
Come to think of it---it was also intermittant at first.. Also when one coil in a dual coil set-up dies ---- same results..
And again when a connection came loose at the coil, and again when a plug wire was not pushed back on the plug suffiently by some total dickhead fool that will remain nameless forever..! Huh.???
Of course you've already checked batt, charging, stator and all their connections right.?..
OK, now, if it's not elect. then of course it's carb related..
A very extreme intake or head gasket leak can cause very poor running, mileage, power loss and vibes.. But, I just don't think so here partly cuz of the slightly rich plugs..
Then there's a dead short somewhere, but that would kill both cylinders not just one..
More info if you have some or check those things and get back..
__________________ "Fill your hands you son of a bitch"
Rooster Cogburn
Last edited by frisco-rigid; 08-16-2008 at 01:50 AM.
Thanks for the kickstart Frisco. I guess my "It's new so it must be OK" troubleshooting theory let me down. I'll re-check everything the correct way and get back to you.
OK Frisco,
I spent a few hours yesterday going over the entire ignition system and came up with nothing! Coil ohm's out fine as do the wires. Used a spark tester and confirmed spark throughout the throttle range (cold&hot). I even tested the tester when I became the ground instead of the plug. I checked all other components and their connections. The only area not checked was the cam position sensor. I also need to check the timing, I didn't have access to a light. Is the clear plug needed? If we're talking a little oil spray I won't worry about it. I also checked motor mounts,vacuum lines, intake seals, etc. I was going to buy another module but I'm not sure what one to get. I plan on installing an EV-27 cam this winter.
You asked what ignition- stock.
As far as the charging system goes- It is charging and all connections are tight. The only issue I have is the connection where the wiring passes through the primary. It leaks oil.
When I pulled the air cleaner to access the intake I found it to be really loaded up with oil. Both rubber hoses from the banjo fittings were split. I thought that stuff should last longer than 6 months. I'm not fond of the Mikuni air cleaner assembly that came with the carb. The stock one and the Arlen Ness don't fit because of the adaptor between the carb and the intake manifold. It causes the backing plate to stand about 1/2 inch off of the heads.
Sounds like time for a compression test. Must admit it sounds like a bad coil causing it to go single cylinder. Top speed on a TC going single cylinder is 56 mph. Guess how I found out.
Did you pull the spark plugs and check them? I ask because I had a plug go bad on my last Sporty and it ran much like you described with yours. Seems like you've covered about evrything else with frisco and Wright...and you can only hope it'll be something that simple. Good luck, Clif
Hey Fat..just another long shot here..but since you mentioned the air filter being LOADED with oil,have you tried cleaning or replacing it? A clogged filter will definately effect performance and mileage...less air getting thru = richer AFR.,etc... while reducing air flow overall,too.
New spark plugs would'nt fix/improve a bad coil,etc. You also mentioned that new plugs lessened the problem DURING warm up but that it quickly returned..ass-sumablely when hot. Rich running engines would tend to act that way...and (noting that you originally mentioned that the problem went from intermittant to constant) the problem could/would have gotten progressively worse, as more & more oil,etc.,accumulated in/on your filter.
You did'nt say that either of your old spark plugs looked different in any way than the other. You just said that old ones (plural) showed a slightly rich condition (equally?) which as others here have agreed tends to eliminate intake leaks,etc. that would cause a lean condition.
If cleaning or replacing your air filter leads to another dead(?)end...try squirting a little water (spray bottle ?) on both your exhaust pipes. If both sizzle/evaporate the water equally..or are equally hot/warm to the (careful here) touch.. at least then you'll know (along with spark plug check) that you don't have a "dead" cyllinder (singular) and can move on to compression tests,etc,etc...noting that all that oil in your filter came from somewhere...possibley just "normal" blow-by,over time..or not !?!
Just "mymind" doing whatever it does up there, again.
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
Sure glad others can add something here cuz I am about out of sugg's..
As far as a wee oil out the stator plug hole, no worry there..
As for timing, ha, it's not just a little spray baby..
Go to "Ignitions" and about 4 pages back you'll see a thread called "Eating Plugs",, The very last post in that thread is my "No Oil in the Face" way of timing..
It is a Perfect way to time after just a wee bit of Prep work, Pictures too, wow..!
I'll be waiting anxiously to hear more suggs and the final answer with halapinyo baited breath ..
__________________ "Fill your hands you son of a bitch"
Rooster Cogburn
"ha,it's not just a little spray,baby".....................................
As mentioned in another thread I saw/read your "no oil in the face"way of timing..copied & pasted for my own future use...very cool.
Meanwhile just thought I'd toss in a great way to static-time a points/condenser ign.,I used to use on Triumphs,that were'nt easy to tune dynamically. Instead of a light or buzzer or eyeball to determine when the points (pre-gapped) were just plain open with the crank degreed where you wanted it,...I'd set a 9-V pocket size AM transistor radio (remember those?) on top of the battery, volume up all the way, tuner set between stations w/o static...when the points just started to break (ignition on) and the radio got static you were right there...noting that the static would go away if you passed that point...in case you/others did'nt(?)know...and/or whatever it's worth these days.
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
Hey,Steel..you're right WD-40 sprayed around there will give you an indication of what's going on. But,man...if you want to see results,try (not for the inexperienced-disclaimer) spraying a little starting fluid around there,not carb throat. If there's an intake leak the rpms will increase,unmistakebley,even with just the tiniest leak.
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
Power loss 
. I checked all other components and their connections. The only area not checked was the cam position sensor. I also need to check the timing, I didn't have access to a light. Is the clear plug needed? If we're talking a little oil spray I won't worry about it. I also checked motor mounts,vacuum lines, intake seals, etc. I was going to buy another module but I'm not sure what one to get. I plan on installing an EV-27 cam this winter. 
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