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No oomph...

  • Thread starter Thread starter mhobryan
  • Start date Start date
M

mhobryan

Guest
I really do realize that this is a bit of a guessing game, but would be helpful to have some direction as where to start diagnosis.

Compared to two 650's I've had, seems to be a dog. Realize the HP and torque spec's are equivelant and the 850 is a little heavier, however this 850 seems significantly slower, particularly on acceleration.

Current state/what's been done:

- 1983 850 GL. 11k miles (assuming the odo is correct and not been swapped)
- carbs cleaned, O rings replaced (PO claimed...based on interaction, and the fact all fasteners replaced with new, I don't doubt)
- diaphrams replaced (not OEM per PO)
- valves adjusted (I did)
- carbs sync'd (I did)
- stock airbox, and exhaust (assuming jets are stock too)
- firing on all four, and all four plugs look good..no signs of running rich or lean - like goldilocks, appears just right.
- fires right up, and NOT cold blooded. in fact, only have to crack the choke a quarter during summer time temps (sometimes not at all) to get it started when cold. Colder temps prefer full choke.
- new air cleaner, appears to be oiled correctly

Low end seems ok, but then has a flat spot in the mid range, then wakes up a bit after 7k or so.

Any suggestions would be appreciated.
 
Wild guess but worth checking. Last week I noticed a flat spot in the mid range. Got to looking around and noticed my valve cover vent tube (or whatever it’s called) had become unattached at the air box. I reconnected the tube and flat spot is gone.
 
Comparing an 850 to a 650 will be just like you describe. The 650 claims 72 HP. The 850 claims a whopping 78 HP and weighs about 80 pounds more. All that extra weight with not much more horsepower will make it seem a bit slow. What you WILL notice is that there is a lot more torque down low. It's quite possible to be doing 20 MPH in fifth gear, turn the throttle and you will start moving faster. Not 'quickly', but it will just keep pulling like a tractor. Downshift a time or three and it will move much quicker, but if you are not in a hurry, shifting is almost optional.

Your 'waking up at 7k' is typical. Some riders report it happening as early as 5500, mine happens about 6k, but it feels like another cylinder has come on-line or a mild turbo boost, but that's just part of the fun of running the engine in the upper band. :encouragement:

.
 
Yep, 6K to 9K rpm is the giggle zone for an 850. Grip it and rip it; spin to win. :twistedevil:

As to whether yours is running correctly, it's impossible to tell from your description. But even if you're putting around like a little old lady, I don't think you should ever feel like it's some sort of lame turd... dunno. Compared to a 650 that's a lot smaller and lighter and has similar HP, the weight will make a difference.

If you're ever close to Indy, we could figure this out pretty quickly... gotta be someone with a good-running 850 around Detroit.
 
Thanks for the input folks. Guess I need to put some good miles on it. I REALLy wanted to take it on a trip to the the UP (that's the Upper Pennisula for you non Michiganders) this past weekend. However, I left a day later than everyone else and had to superslab it up I-75 solo. If I had had the opportunity to take it on even one long Sunday ride prior, I probably would have done it, however, all my miles have been local, little highway. I have learned that city and hwy riding put different stresses on a bike...some little gremlin could have been waiting to put me on the side of the road ruining my weekend. So I took my '04 Softail with 54k miles. My softail definitely feels like it has much more exceleration. The Softail weighs a good 200 lbs more, and even though the stock torque is higher, the HP is fairly equivelant. Granted, the bike is not fully stock...have mild cams, bigger air box, rejetted carb, and pipes. But with the significantly heavier weight, figured it would all even out.

I realize this is like comparing apples and hamburgers.....and is practically impossible to trouble shoot without hard data. I just expected it to have more acceleration. It doesn't feel like a 12.5 second quarter mile bike...feels like more like a 14 second bike. Just going to have to check out a few more things, and if all else fails, dive into the world of pods, pipes and carbs.
 
air filter over-oiled? maybe try removing it for a quick run.
check the timing w/a light.
partially blocked fuel filter? check flow by removing the line at the petcock and/or carb

that's all i got. if you'd like the bike to be a bit snappier, you can try going -1 on the front sprocket. cheap enough ( $14 for mine), but realize the bike may feel a bit buzzy at highway speeds.
 
standswithabeer said:
air filter over-oiled? maybe try removing it for a quick run.
check the timing w/a light.
partially blocked fuel filter? check flow by removing the line at the petcock and/or carb

that's all i got. if you'd like the bike to be a bit snappier, you can try going -1 on the front sprocket. cheap enough ( $14 for mine), but realize the bike may feel a bit buzzy at highway speeds.
Click to expand...

It's a shaft drive bike, so changing a sprocket isn't in the cards.
 
and that's why no one should listen to a guy with only 12 posts. : )
 
Thanks for the suggestions folks. FWIW, I did by pass the fuel filter last night.... no difference. Does not appear to run lean...at least at idle. Almost no choke required in the summer time, and it idles fine. Plugs look decent too....but then mostly around town driving. Next will check for airbox leaks...my theory is that as I get on it, it sucks more air making it run lean.

BTW, my wife has ridden it, and also thinks it is definitely slower than the 650's,so not just my perception.
 
".....diaphrams replaced (not OEM per PO)"

I'd doublecheck these, to make sure piston thruhole is oriented correctly
 
I got a big part of it's oomph back!

Felt to me like it might be running lean, so thought I'd check out the airbox seals. One on the right side was missing a piece of the seal, replaced it with some weather stripping, and noticed a noticeable improvement when I took it out for a quick test ride. Took the left side off and there was none (not sure if they designed it that way or not....) so added a thin strip, and again, a noticeable improvement! It now has the acceleration of a motorcycle - also seems to be running smoother too.

I'd say it's about 90% there - have a new petcock on order, and will replace it by next weekend. Want to take it on an over-nighter my wife and I are doing in Marshall Michigan on Sunday (cool little B and B there, and walking distance to town as well as a micro brewery .... Dark Horse IIRC).

It is fun bringing these bikes back into spec....now I look forward to enjoying the fruits of my labor!
 
Good to hear that you have it running much better, but had to comment on this:
mhobryan said:
Just going to have to check out a few more things, and if all else fails, dive into the world of pods, pipes and carbs.
Click to expand...
This is something you should not attempt until you DO have it running correctly, or you will be chasing your tail, trying to find out what's wrong and why it's not running the way you want. If you at least start with it running well in stock form, you have a baseline from which you can make changes.

And keep in mind what I posted in post #3. The 650 is about 80 pounds lighter with virtually the same power, so it will feel quicker. Off the line. After about 50 MPH, there is simply no replacement for displacement. And, if you plan on any 2-up riding, there is a LOT more room on the 850. :encouragement:

.
 
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