I just swapped belts on my 900 motor, and it is turning over but not wanting to fire. it sounds like im off a tooth but all the marks appear to me to be lined up. i have done this before and not encountered this problem. pics for a sanity check before i break out the compression tester.....
(http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs008.snc4/33740_949392058574_3314554_51445791_121930_n.jpg)
(http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs621.snc4/58120_949391764164_3314554_51445779_5448636_n.jpg)
(http://sphotos.ak.fbcdn.net/hphotos-ak-ash2/hs124.ash2/39552_949391559574_3314554_51445767_3371135_n.jpg)
anyone see anything amiss?
Everything looks slightly off, but by about the same and in the same direction.
I wouldn't think that's the issue.
ya, i took the pics and noticed, bumped it all, now it all looks perfectly aligned... [bang]
Crazy question, if you pulled your plugs to turn the motor, are they back in and wires hooked back up?
...and you checked the kill switch? ;D
hah never pulled the plugs, and it is trying to fire, but coughs out and dies
so compression is 110 and 130, and both plugs are firing......
:'(
the marks lined up with the old belts as well. so confused.
Do you have plenty of fuel ? Try taking out the plugs and squirting some into the cylinders.
crankshaft off by 1 rotation?
Quote from: floyd turbo on October 03, 2010, 04:29:21 AM
crankshaft off by 1 rotation?
If the layshaft mark lines up it can't be off.
How long since last start? Seems like there's been a lot of fuel delivery problems lately.
From what you have shown us your timing is correct. Going on the assumption that the bike was running well before the belt change and having nothing to go on besides your compression figures (a little off, particularly the 110 cylinder) and the test was done properly (throttles open, 4 revolutions) I'm going to guess you flooded the engine and the spark plugs are not happy. Try some new plugs and see what happens.
Did you maybe pinch a fuel hose when you lowered the tank after the belt change?
Quote from: iamhybris on October 03, 2010, 07:48:46 AM
Did you maybe pinch a fuel hose when you lowered the tank after the belt change?
Yeah, check that too.
...but the bowls shouldn't empty in the time it takes to change belts...it should at least start and run.
howie's suggestion of a plug issue is more likely, or if it sat a long time since you last ran...it bad ethanol fuel.
was running just fine before. new plugs and no change. redid the compression (throttle open [bang]) and got 140 vert 130 horiz. im about to just throw the old belts back on in a hopeless act of desperation...
Quote from: kingmoochr on October 03, 2010, 10:23:12 AM
was running just fine before. new plugs and no change. redid the compression (throttle open [bang]) and got 140 vert 130 horiz. im about to just throw the old belts back on in a hopeless act of desperation...
how would that fix the problem?
well so far i havent found a problem, other than not wanting to run [bang]
Belts are not a problem with your new readings. Recheck everything. You might be overlooking something simple, like a vacuum hose that was disturbed or a wire that was knocked off. Is your bike carburated or injected?
fcr'd. it really sounds like the timing is off, but there is nothing to indicate that it is...
How long did it sit between the last ride and the belt change?
The gas is a week old.
That isn't the problem.
The marks line up correctly so it doesn't seem like you screwed up anything there.
Now the question is: what did you move/touch/disturb when changing the belts?
Are all the wires connected (check if they're loose). If you have a fuel petcock is it open? Did you lift the tank to do the work, could some "crud" have made its way into the filter and be clogging up the fuel system?
When this happens to me it helps to just walk away for a while do something else and then come back. That's when I have an "ah ha!" moment and realize what a retard I am ??? :-\ ;)
Check to see if you are getting full voltage at the plugs. If you have no spark, then it's electrical. If you do have spark, then it's got to be fueling.
Quote from: humorless dp on October 03, 2010, 04:31:10 AM
If the layshaft mark lines up it can't be off.
i was thinking that there might be a remote chance that when the belts were off and if both cams were turned to were the valves are all closed and somehow the crank got turned off of the mark and then back to the mark in the wrong direction. would that not screw up the ignition timing?
Quote from: floyd turbo on October 05, 2010, 08:36:50 AM
i was thinking that there might be a remote chance that when the belts were off and if both cams were turned to were the valves are all closed and somehow the crank got turned off of the mark and then back to the mark in the wrong direction. would that not screw up the ignition timing?
If the layshaft mark and the two cam marks line up all is good. The direction you turn the crank is immaterial although direction of rotation is always best to account for gear lash.
If any one of those marks does not line up when you install the belts all bets are off.
maybe i just dont understand the way the ignition system works. actually i know i dont. but it was my thought that if the crank was out by 360 degrees the plugs would be firing on the exhaust stroke rather than the compression stroke
Quote from: floyd turbo on October 05, 2010, 09:29:06 AM
maybe i just dont understand the way the ignition system works. actually i know i dont. but it was my thought that if the crank was out by 360 degrees the plugs would be firing on the exhaust stroke rather than the compression stroke
That's true. On the Ducati engine the ignition either has a waste spark meaning it fires in both places, or it is keyed to the layshaft position. There are also two tdc marks. One for vertical and one for horizontal.
The layshaft mark can only line up in the correct position which is why it's there and why I suggest using it for the belts.
thank you. everything makes sense now.
If I let my 900 sit for a week it is an absolute mothermake the beast with two backser to start. If I don't ride it for a month then it will require starting fluid. My guess is its the wonderful ethanol fuel separating in the float bowls. if I ride it a few times a week it fires on the first revolution.
Quote from: Porsche Monkey on October 07, 2010, 04:59:03 PM
If I let my 900 sit for a week it is an absolute mothermake the beast with two backser to start. If I don't ride it for a month then it will require starting fluid. My guess is its the wonderful ethanol fuel separating in the float bowls. if I ride it a few times a week it fires on the first revolution.
Same with my 750 - though after I get a hellacious backfire it starts right up. I always figure it's clearing the clyinders :P
Quote from: MongoReturns on October 07, 2010, 09:18:45 PM
Same with my 750 - though after I get a hellacious backfire it starts right up. I always figure it's clearing the clyinders :P
Yup ill usually get a few flames out of each pipe a couple times while it clears its throat.
Check for spark?
Dead coil?
Blown Fuse?
Voltage Regulator?
After repeated starting attempts, plugs should be wet with gas. Are they?
Just throwin spaghetti and seeing what sticks to the wall.
I changed the belts once in my ST4 and encountered the same problem. I pulled the plugs to observe the spark and it sparked as it should. Put them back in and nothing even close to running happened. I removed the belts and turned the engine through one revolution and re-installed the belts and it ran like a top.
Think about it being a 4 stroke and the crank rotates 720 degrees for each combustion cycle. If the crank got rotated (360 degrees) during the valve adjust/belt replacement the spark could occur on the exhaust stroke vice the compression stroke. Remove the belts and rotate the crank one revolution ,replace the belts and it should work fine. At least that is how I rationalized what happened to my bike.......
Yes, but the crank is geared 2:1 to the layshaft which has the central/ lower pulley attached to its end, so if the mark on the lower pulley is positioned correctly the crank and the ignition timing will be correct - unless the motor has been pulled to pieces.
The two cam pulleys are the same size as the lower pulley so if the marks line up all is good.
The thing is if he has spark and fuel
the only thing left is timing ...i know the marks line up but this has to be it
OP you have checked for spark and fuel correct ?
lets not overthink this ....it only needs 3 things to run spark-fuel-air
Any updates? It might just be coincidence, but when my bike sits for extended periods, and the weather is a little cooler like now, it is a b!tch to get started. Always has been. Like today, I had to hold the throttle at 3/4 open while cranking for about 20 seconds before it fired. Have you tried holding the throttle wide open while cranking?
mitt