Won't run

[Downer]

Hey guys new here I'm sure you have heard it before bike won't run got spark engine cranks connections are good and grounded battery is charged but engine just won't fire bought it off a friend of a friend that rode it down from oregan to so cal on the way back it just broke down checked the plug wires one was fried replaced them both and caps now got spark to both any other ideas on what I need to do? Thanx in advance

 

[DetroitMuscle07]

Have you checked compression/valve clearances/timing?

 

[Downer]

No not yet but would that keep it from starting? I thought that would just make it run crappy I'm not sure I'm new to the mechanics thing he did say that it might be due to over filling the oil

 

[Downer]

Also it's a 77 with points that might help to tell that

 

[Downer]

I mean I have done the timing but not checked compression or valve clearance

 

[Downer]

Any other ideas? Thought I had points wires crossed that wasn't it I don't want to use starter fluid but I'm coming to my last resorts every thing seems in order can't figure it out sorry just venting

 

[TwoJugs]

Shoot some starting fluid in the carbs and try it then. If it still doesn't start or at least pop check compression. If it has compression and is sparking close to time then the fluid should make noise. Of course spark too.

 

[xjwmx]

If you have spark and the timing's right, check compression. Leave the tester attached for a few good cranks to get the highest reading, and hold the throttle all the way open. If compression isn't below 110 or so, then it has to be carbs, or fuel flow.

 

[Downer]

Well I put a little gas in the spark plug holes I figured that would be better than starting fluid I've been reading bad storys about that anyways I put the gas it the holes and cranked it and it just backfired once and that was it tried changing point connections and nothing

 

[PhatTony]

If you try and make it run for a long period of time with starter fluid it will eventually melt down. One squirt will not destroy anything. Dropping gas down the spark plug hole with usually only get you one fire. Starting fluid in the carbs will get you two or three fires.

Spark, timing, compression and fuel mixture if you have all of these it will run.

Spark good
Timing good. "if it back fired through your exhaust it sounds like you have the leads switched on the points. I believe you can put both leads on one point and you could run in wasted spark But I am no expert on points! Someone else needs to chime in on that one.
Compression ???
Fuel Mixture ???

 

[5twins]

Since you're dealing with an unknown problem here on a bike that won't run, you should check everything - do a complete tune-up. It needs to be done in a specific order because one thing can affect the next. Here's the order .....

- cam chain
- valves
- points gap
- timing
- carbs

A valve may have gotten tight. That would cause it to die and make it hard to start, maybe not start at all. These bikes like their timing and points gaps set exactly. If they're off, it would be hard to start and, again, may not start at all.

 

[Downer]

shouldent the right points go to the right ignition coil and the left to left? thats how i had it when it backfired?

 

[5twins]

The top set of points (right cylinder) should hook to the right coil, bottom set to the left - but that's assuming the advance rod is installed correctly. Did you have the advance rod out by any chance or even just the disc or point cam on either end removed?

 

[Downer]

how would i check if the advance rod is installed correctly?

 

[5twins]

The little cam on the points end and the little disc on the advance end have locating pins that lock them into position on the rod. These must both be facing in the same direction, not opposite to one another. If they're opposite, your timing will be 180° off.

 

[Downer]

5twins can I adjust the cam chain on a non running engine and when I do adjust it it needs to be on the t mark right? I'm going to use your order of things to check

 

[5twins]

Yes, you can adjust the chain with the motor off, just follow the instructions in the shop manual. You don't set the engine at any specific point like TDC to do this, instead you rotate it slowly by hand in the direction of rotation (CCW as viewed from the left side) and watch the plunger movement in the adjuster screw. It should move in and out slightly, coming out flush with the adjuster screw but not past it. Unfortunately, it can be difficult to get a good adjustment this way. That's why most of us check it with the engine idling. You can get it good enough this way until you can do the running check. Just make sure the plunger has some in/out movement, if it doesn't move at all, it's set too tight.

 

[Downer]

Is there a good thread on adjusting valves also can this be done with a non running engine? And I don't know if it's right but when I turn the stator it wants to fly by the f mark with plugs out and even almost past the t mark but with plugs in I can get it pretty close to the f mark just wondering if that would be because the cam chain is not tight enough

 

[5twins]

Valves must be done on a non-running, cold engine. You can't do them while the engine is running and you're not supposed to do them on a hot engine because the parts are expanded from heat. Clearances set on a hot engine may not remain the same when it cools off. The adjustment specs are given for a cold engine.

It's normal for the motor to want to spin past the timing and TDC marks. You have some valves partly open and the valve spring pressure on the cam will want to rotate the motor. Use a wrench or breaker bar on the rotor nut, not a ratchet. You need a tool you can stop the rotation with and hold the nut, something that doesn't ratchet.

It appears this is all quite new to you. You need to read through a shop manual. It will explain how to do all this tune-up stuff. There's a factory shop manual on-line here .....

http://www.biker.net/

It's free to view or download and will walk you through all the tune-up stuff.

 

[Downer]

I have a haynes book but it's not that informative but I continue to thumb through it I'm looking for more of a step by step kinda thing but again I'll check it out thanx for the help so far I'm sure I'll have more questions to come