Seems to lack the "oomph" it had...

[CdnDave77]

Morning all..

 

I have an 83 Std, that was new to me last year. I love the old girl and used it as often as I could on my daily 40 mile commute to work until the snow flew. When spring finally reached this part of the world a few weeks ago, I put the charged battery back in, changed the plugs (all looked good at the time), oil, etc. I had stored it with some Seafoam in the fuel, and have run 2 tanks through it in the last month.

 

My issue is that it just doesn't seem to have the top end power it did. It doesn't accelerate nearly as fast as it used to. The exhaust note seeems to be ever so slightly lower (not a bog though). Hills are now noticeable. It's not the clutch slipping as the rpms don't climb as rapidly as they used to.

 

Thinking it was carbs, I dosed her again with another can of Seafoam and went for a hard run on some quiet backroads. It accelerates, not with the "Jeez, I'd better hold on tighter" feeling it used to. It attained and easily held 150 km/hr (90-95 mph), and I backed down before it did.

 

Should it get to that speed running on 3 cyclinders ? All four header pipes are hot. No popping or burbling at all on a decelleration. I changed the plug caps (trimmed the plug wire ends too), with no improvement. All 4 slides move evenly and smoothly when you hit the throttle and nothing is impeding their travel throughout the whole range of movement (checked each slide with my finger while not running). All 4 plugs are a nice tan colour. Air filter is freshly cleaned (re-usable foam) & re-oiled (K&N oil). Fuel filter was replaced when I got it, and looks clean now.

 

Could it be timing - the boost sensor ? I am pretty sure I didn't gain 200+ lbs over the winter.

 

Any thoughts would be muchly appreciated.

Edited April 20, 2009 by CdnDave77

[Gearhead]

Well, you've checked a lot of good stuff. Just a couple wild ideas:

 

1) Watching the slides move "evenly" isn't a good test. Mine were doing that, to the eye, but 3 of four diaphragms were quite bad. Rreplacing the slides / diaphragms didn't pick up THAT much top end, but some. If yours are original I'd be surprised it they're still sound.

 

2) K&N oil is made for K&N filters, not foam filters. They make foam filter oil. A K&N filter is a lot thinner and less dense than a foam filter. I don't know, but is it possible the K&N oil causes the foam filter to be restrictive?

 

3) If all four pipes are hot then you're not missing on one cyl, at least not all the time. Have you started it cold, then shut it down and checked the pipes after just 20 or 30 seconds to get a read on how fast they are heating up?

 

Jeremy

[CdnDave77]

Actually, I have had several shops tell me that K&N oil is fine to use on re-usable filters. I've done it for years on other bikes and never had an issue. (My old 750 Maxim was just as finicky as the Venture for needing a "restricted" airflow).

 

I should have specified earlier that yes, I did check the cylinder temps from a cold start. I responded to another helpful email moments ago that I was frantically fumbling all over the engine trying to sense if one cylinder was remaining cool longer than the others. I will redo it when I get home from work, but I couldn't discern any difference between the 4 cyl's on Saturday. A bad cylinder should lead to a fouled plug, wouldn't it ?

 

I highly doubt the diaphragms are original. The bike has had quite a few owners, but it looks like someone along the way took care of the old girl. The carb slide covers have obviously been on and off a few times by the look of the capscrews. My next step is to pull them off and try some liquid electrical tape.

 

If the boost sensor was faulty, or had a vacuum leak in the line going to the sensor, would the rpm's fail to climb as fast as they should ? What other symptoms would exist ?

 

Thanks again.

[BoomerCPO]

Maytag has a big Sale on drive belts....P/N for fit up on 1st Gen's iz AntiqueBr1541.....

 

 

Boomer....Doing his part to make folks smile...giggle....and fart.

[CdnDave77]

I guess I could retitle the thread "Help... my 26 yr old 1st Gen is running almost as bad as a 2nd Gen".

 

 

 

That was funnny though, Boomer. Especially as my bike is white !

Edited April 20, 2009 by CdnDave77

[Squeeze]

I'd concentrate on the Spark Advance Devices and Hardware for the next Step. That's measuring Vacuum Sensor Output Voltage, check Vacuum Hose for leaks or a clogged Restrictor and finally TCI if eveything else checks out good.

[CdnDave77]

Ok, so it is pouring rain and cold today, but my garage where the bike is doesn't have lights. I have to wait until I can get a couple of hours and trace that vacuum line.

 

Thanks for the suggestions all.

[bobcat]

Just for sh*** and grins I'd replace the plugs...

[CdnDave77]

Ok, rain stopped (for now) so I had the ability to pull the vacuum line off the carb and check if the boost sensor and TCI were functioning.

 

In what my wife would refer to as a "questioningly intimate moment" with my motorcycle, I applied vacuum to the boost sensor line (ie: "sucked it") while holding the bike at 2000 rpm... it revved up. To ensure it wasn't me adding throttle due to the heat of the moment, I replicated it again at idle... rpms went up - exactly as they are supposed to.

 

I tried to measure the amount of vacuum being generated at the Carb #2 body, but I don't seem to have a fitting small enough to connect my vacuum gage. I'll raid the supplies at work tomorrow to see if I can get something close - but I couldn't discern a vacuum or pull at all with my finger. Since my better half was already eyeing my suspiciously, I wasn't about to hold my tongue on it.

 

With that nozzle/port open to atmosphere, shouldn't the idle have changed ? Or a noticeable difference when I revved it ? Nothing was any different. What the heck could have blocked it ?

 

I await further wisdom...

[BoomerCPO]

I sure wish I had an answer for your problem but I only own a trouble free 2nd Gen.....

 

 

Boomer....who never plans on having oral s*x with his motorcycle.

[Squeeze]

Vauum Sensor/Spark Advance sounds good so far. Normally, Idle Speed could change by opening the Air Connector, sometimes Idle changes, sometimes not.

 

I'm sorry, it may sound bumb, but how much Filter Oil did you spent after you cleaning the Filter ? K&N Filters get glogged easy by using too much Oil and thereby restricting Air Flow. I'm not suspecting this, but i gotta ask.

[Marcarl]

When you take off the vaccum line, spray some carb cleaner, MotoMaster is the best I've found, into the vaccum port. Wait 15 or 20 minutes and do it again. If it won't take a spray it is plugged, can happen over the winter. Use a thin brass wire to start a small hole though which you can force some cleaner, wait and then try it again. A little air pressure sometimes also helps in the process.

[CdnDave77]

As for the oil on the air filter, it was just a very light coating. It's certainly not a bad suggestion, but I have my doubts that it is restricting the airflow that much. If it were, it should be struggling somewhat at 5000 rpm, and not just the ramp up from 2000 to 5000. It accelerates, just slower than it used to. I'll pop the filter off, wash it again, and use a different oil.

 

When I had the vacuum line off, I did give the carb vacuum port a bit of a probe with a torch cleaning rod. I am unsure of exactly how far the rod should could into the carb throat, but I did hit resistance after a bit. I didn't want to force anything until I could look at a diagram and figure out what I am hitting and how deep into the carb it is. I shot some carb cleaner (same brand) into it, let it sit for a few, and then applied another short blast. I'll try to get a smaller ID adapter today so I can get my vacuum gauge on that port tonight.

 

If I put a small blast of air in that port, could I damage anything ? My diaphram is intact and I would like to keep it that way.

 

The pictures in my service manual are somewhat grainy (at best). Does anyone have a good diagram of an 83 Carb (they were different the first year, correct) ?

 

And although I am not doubting your word, Boomer... is there such a thing as a trouble-free motorcycle ? Other than the Honda XL-75 that I had when I was 9, I have never heard of such a thing. An older gentleman 2 streets over from my house has a 2nd Gen... offers to trade me even for my old girl every time I stop by. Wonder why ?

[timgray]

Nobody mentioned this....

 

Did you check the Carb Sync?

[Condor]

Nobody mentioned this....

 

Did you check the Carb Sync?

 

Beat me to it.....

[CdnDave77]

I checked the synch on the carbs when I first got it running after the winter storage (a month ago),all 4 cyl's were very close to where I had set it in August after getting the bike. But it is very quick to check again. I'll post the result back after I do it, but it likely isn't going to be tonight : raining and cold again today.

 

I am crossing my fingers that the carb cleaner in the vacuum nozzle worked some magic overnight. The more I think about it, the more there shouldn't be anything "stuck" in that nozzle as the "vacuum" flow should have prevented anything from the carb going in there. The service manual don't even show that nozzle/port in any of the illustrations... it should go right to the throat, no ?

 

Thanks for the suggestions, fellas...

[slick97spirit]

Boomer....who never plans on having oral s*x with his motorcycle.

 

 

 

Boomer, you are a riot. This one should go into the classics forum!!!!

[mbrood]

I would think any carb port "restriction" would be easy to check... fire up the bike and pull the vacuum hose off the carb and cap it with your finger... even do the same with her at 2k rpm...

[Neil86]

I think you will find the 83 uses "ported vacuum" to operate the pressure (boost) sensor. In other words, the vacuum is tapped ABOVE the throttle plate, therefore it will be minimal at idle. Pretty common on auto carbs.

http://autorepair.about.com/library/glossary/bldef-626.htm

 

Hook up a vacuum gauge/manometer to the port and raise the rpm....see if it starts showing vacuum with plates opened up abit.

 

As for the power issue.....if you still have the YICS chambers operational, perform a vacuum test on the hoses and chambers.....they tend to crack apart due to heat and vibration and cause vacuum leaks, poor performance (leans out carbs).

[cowpuc]

Also dont forget the obvious.. Put the bike on a stand and spin the tires and see if your brakes are binding.. CHeck your pipes for dings and also check them for mouse nexts - remove the muffs and see if she comes up to speed.. Spray carb cleaner on Vacumm lines while its idling and if the idle changes you gotta leaker. Check air pressure in your tires. RUn it without the air filter in it and see if its being chocked off..

'Puc

[CdnDave77]

Mr. Marcarl...

 

After letting the carb cleaner sit overnight in the vacuum port, I gave it another blast of spray when i got home last night. I had the bike running and there was still no discernable vacuum. Spraying the carb cleaner in didn't affect the idle so it obviously wasn't getting through -it just ran back at me. I gently probed the port again with a tiny drill bit and after a minute or so, I could hear a faint whistle. Another good shot of carb cleaner did the trick. (I acknowledge I blew whatever it was directly back into the carb, but I am hoping the carb cleaner carried it through). There was very definitely vacuum when I brought it up to 2k rpm.

 

So, vacuum line to the boost sensor operational once more. I did a quick check of the sync just for insurance, ever so slightly tweaked 3/4 to 1/2, and considered it done. I rode it into work today and it is most certainly back to where it should be.

 

Was it likely just varnish from old gas ? I'll never know likely.. but you were bang on the money, Marcarl (pm coming your way). Thanks to all for the assistance. See you on the road.

[Dragonslayer]

My next step is to pull them off and try some liquid electrical tape.

I've found that , and as per Muffinman's advice, that Plasti Dip in an aerosol can works better. Spray the inside of the diaphram the spray the outside. Hang upside down and let completely dry before reinstalling. The entire surfaces inside and out get an even coating so the diaphram is not hard in spots and pumps in and out more consistantly.

I found the product at Northern Handyman.

[CdnDave77]

Thanks for the tip... but when I took a look at the diaphrams last night, they appear to be relatively new. The PO (or one of the PO's) must have changed them not that many miles ago as there are no lines, bridge marks, white/stress areas, etc. Certainly no holes.

 

I'll keep it in mind for when i do need it though.

[Oldgold]

After reading this thread I checked the vacuum on my 83, low and behold no vacuum at any rpm. Several squirts of carb cleaner and a poke with a small pin opened it up, lots of vacuum and definitely more "oomph"

[timgray]

Just for others that want to check, can anyone post a photo or describe exactly where that port and hose is?