Topic: Bike lost most of its power and now wont start

[singedebile]

'75 550f

The engine was running great since I have had it (about 1000miles and a bunch of months). I lost a bunch of power when i was on the highway so i took the first exit and limped a dozen blocks before my clutch cable snapped. The bike had enough power to pull away from stoplights but it struggled a bit (but didnt stutter). Now i have replaced the clutch cable and rebuilt the front brakes and went to try and start it to get some ideas and it almost rumbles a bit sometimes but wont catch, ..backfires every once in a great while as well.

When I last drained the carbs only a little sediment came out.

I was planning on pulling the carbs (for the first time) but I feel like I should not add variables until i try some other things. Especially as the bike was running really well (idles happily at about 1100rpm), I dont have a carb sync etc.. so I dont want to mess up any settings.

From what I understand it might be a fuel delivery issue.



Whats the order of events that I should try?

if I pull the gas hose how much should be dripping out?
I do have some inline filters, but they seem well installed, though they likely will need to get replaced..
I have already spent a bunch of money (for me) and I would like to do what I can that wont involve buying until I know I have to.

[TwoTired]

I am always amazed at how well the bike responds to a regular tune up schedule.

You looked at the spark plug tips yet?

Looked at the points? Setting?

Does reserve setting work?  What is the tank's fuel level?

[singedebile]

It was give a full tuneup about a 1000miles ago by a local vintage mechanic

The reserve hasnt worked as long as i have had the bike (just acts like the main)

I havnt pulled the plugs, I will try to find a car and drive out to the auto parts store for the right size spark plug socket

I havnt figured out the points yet.. but you still think it might be an issue if it was running well before? I guess maybe the plate could have slipped?

update*
bought some tools, going to call it a night though. Ill post again once i have tried a few more things

[TwoTired]

I'd get a Honda spark plug socket, like what came with the tool kit, if I were you. It is bell mouthed to clear tunnel obstacles.  You can break spark plugs or cross thread the head holes if you aren't careful with a standard deep well.

I'd at least look at the points.  The cover has a whooping two screws!  Anyway you have to be certain there is spark at the plug tips before condemning the carbs.  Nice to know if the carb bowls are filling, too.

Are you out of gas?

Cheers,

[singedebile]

Alright a quick update
(first i never implied a fear of two screws, i have just never done the points/timing before which was made obvious by the fact i needed still to buy gauges etc..  I didnt have the time.. what am I supposed to instantly realize after looking at the points without doing a bunch of reading, I Have to get up at 4:30am for work and needed to eat dinner)

Today after work I got another chance to work at it and "iron out" a couple possible culprits. My moms longtime boyfriend was here, he has allot of wrenching experience but he is not the most precise worker.. so despite his help and enthusiasm i am happy to work on it now in a more deliberate and methodical way now that he is gone)

-Of course there is fuel ! (i had to take the train to work the past two days, despite a lack of time there is allot of motivation.. the beautiful weather helps too)
-checked to see if the fuel was getting to the carbs (through the possibly clogged petcock/tank screen and possibly clogged inline filters and through both the reserve and main settings)
-checked to see if there was spark at plugs 1 and 4 (i will have to order a proper socket to get at the other plugs..  though if the problem was simply 2&3 i feel it would be likely the engine would fire somewhat (remember the engine just cranks without catching)
-Double Double checked fuses
-Also you could smell gas as I tried cranking it.. and there was gas smell from inside the cylinders
-the battery is fully charged and the bike cranks well
-Started peaking at the points, they looked roughly ok but maybe not but i have some questions
   
    -How important is a 'points file' as mentioned in the clymer (they say to specifically not use emery cloth or fine sand paper) as they did not have any or know what I was talking about at pepboys
    -The points themselves looked to be 'recently replaced'
    -Doing the static test the clymer doesnt mention which direction to turn the engine crankshaft.. assuming with the arrow are the points (for whatever cylinder pair your timing) supposed to be open then close when they reach the first TF 1-4 mark (sorry to spell it out but I just want to be sure I understand this before I mess with the points more) I noticed there seems to be a mark on either side of the TF 1-4 and another two for the TF 2-3

sorry Im getting a bit delirious again (i hope what i wrote makes sense and that i didnt come off as too frustrated), I am going to find some food and hopefully atleast do a proper static timing before i got to sleep tonight

thankyou if you made it this far and for the help.. i know we can figure this out

[kaceyf2]

Hya there Bro, you turn the engine a tad at a time with the kickstart, it will give you the right direction, there is also a chance of a knackered condensor ... each condensor serves two cylinders like the points, so if one goes you got two cylinders out. most 750's will start and run on three cylinders but not two...
they are so cheap as are the points that you may as well get a set of each..  Your absolute best bet is to get a manual, its the best investment you can make... I promise.

[singedebile]

another quick update, with some good news

I removed the airfilter and replaced the two spark plugs i could get to and she unhappily starts!!!   I drove her down the block she backfired a couple time and doesnt have much power and the engine dies below 2000rpm BUT SHE RUNS ... I am going to do a good static timing and try it again.

[singedebile]

Hya there Bro, you turn the engine a tad at a time with the kickstart, it will give you the right direction, there is also a chance of a knackered condensor ... each condensor serves two cylinders like the points, so if one goes you got two cylinders out. most 750's will start and run on three cylinders but not two...
they are so cheap as are the points that you may as well get a set of each..  Your absolute best bet is to get a manual, its the best investment you can make... I promise.

hmm ok, I was using a 23 mm wrench to turn the crankshaft.. but the kickstarter will ensure I am doing it right. I would have thought that she would run on 2 cylinders...  maybe what you say could still be the problem. I will test the condenser as the clymber says but I maybe be looking to get new ones just in case. And it would make sense if the condenser just died.. the other puzzle pieces would fit

so..
1. proper static timing
2. get those last 2 spark plugs out and replace them along with the condenser. I again will be gone for several days starting tomorrow and tonight is my last chance.. I will order the spark plug socket somewhere and atleast have that when i get back. But I will still do the timing and anything else I can tonight

[TwoTired]

The owners manual. Or the Honda shop manual has all the info you need to set timing and do the routine 3000 mile tuneup schedule.

In it, they explain that the T mark is to adjust tappet. and the F mark in when the spark should occur.  The spark occurs when the points open.   The crank turns in the same direction as the rear wheel would to move the bike forward. Looking from the right side of the bike, that's clockwise.

1&4 spark from one coil, 2&3 spark from the other.  There is a set of points from each.

For the engine to run, you need compression, an air fuel mixture, and correctly timed spark.  An engine that doesn't run is missing one of those 3 elements.  You need to find the one that's missing, or diagnose by process of elimination by noting/verifying what you know is working of the three.

If you have i running, then check the head pipes for heat.  Cold pipes = dead cylinder.  Burnt/blistered fingers tell you which cylinders are working.

Cheers,

[singedebile]

thats exactly the wording and explanation i needed thankyou,