GS674 won't start???

[Guest]

Hello

I have a 550/650 hybrid motor and can't get it to start, no sputter or anything resembling combustion. I do have spark, I BELIEVE that I have compression, (Compression tester has been ordered), and BELIEVE fuel is getting to the cylinders. I have tried starter fluid with no success at all not even a single power stroke. the test start was done with the pod filters off, Here is the list of parts that I am working with;

-rebuilt GS674 Motor, cams set properly as per Dealer service manual.
-4-1 Mac header into 2 megaphones
-BS32SS carbs jetted with dynojet stage 3 jets/neadles ect, & K&N Pods
-Dynatek 2000 for ignition

[tkent02]

This is a newly assembled engine, first time trying to start it? So you primed the carburetors and nothing? Adjusted the valve clearances correctly? Ignition timing is right? Not mixed up spark plug wires or anything?

If starting fluid won't even get a pop, there's something very wrong.

I'd triple check the timing. Could be firing on the exhaust stroke or something goofy like that.

[blowerbike]

rebuilt GS674 Motor, cams set properly as per Dealer service manual.

you have a Frankenstein engine so i would assume your cams need degreed and may be off a mile....just a guess.

[tkent02]

rebuilt GS674 Motor, cams set properly as per Dealer service manual.

you have a Frankenstein engine so i would assume your cams need degreed and may be off a mile....just a guess.

Even so, if the valves didn't hit the pistons it would at least fire, wouldn't it?

[ashdricky]

This is a newly assembled engine, first time trying to start it? So you primed the carburetors and nothing? Adjusted the valve clearances correctly? Ignition timing is right? Not mixed up spark plug wires or anything?

If starting fluid won't even get a pop, there's something very wrong.

I'd triple check the timing. Could be firing on the exhaust stroke or something goofy like that.

Timing could be off, I will check the wires again,

rebuilt GS674 Motor, cams set properly as per Dealer service manual.

you have a Frankenstein engine so i would assume your cams need degreed and may be off a mile....just a guess.

I suppose the cams may be off, I am using 550 cams, and never took the sprockets off of the cams.

[Nessism]

Cam notches should be pointing at each other with engine at 1-4 TDC. It's easy to get the cams 180* out too (don't ask me how I know).

[blowerbike]

i guess my point is....
you built a neat engine...it's a shame to have your cams off in unknown land.
hell even a dead stock engine benefits from puting the lobe centers in the right place and separation.

[ashdricky]

i guess my point is....
you built a neat engine...it's a shame to have your cams off in unknown land.
hell even a dead stock engine benefits from puting the lobe centers in the right place and separation.

I agree with you, my thought is to check the easiest thing first befor pulling out the cams,

Cam notches should be pointing at each other with engine at 1-4 TDC. It's easy to get the cams 180* out too (don't ask me how I know).

if my cams were off by 180, the motor would still turn over without valves hitting the piston?

I just went through the timing procedure and reset everything. there are two "T's" one between carb 1 & 2 and one between 3 & 4 I understand that these are breathers is it acceptable for them to be open to atmosphere?

[ashdricky]

After resetting the ignition timing I was able to get what sounded like several powerstrokes, then nothing, sprayed ether in the carbs and not much happened. I did shine a light into a cylinder and did watch the exhaust valve close on an exhaust stroke, which makes me feel as though cam timing correct. I will have to sleep on it and try again tomorrow, like a fool I removed the electric starter so I have to kick this thing to death...

[wymple]

I find a motor that has the cams retarded by about 45-50 degrees won't even pop a lick. If you are advanced too far it will certainly let you know with a bang. We just went thru this with a XS650 Yamaha, proper cam timing and 1 kick.

[tkent02]

After resetting the ignition timing I was able to get what sounded like several powerstrokes, then nothing, sprayed ether in the carbs and not much happened. I did shine a light into a cylinder and did watch the exhaust valve close on an exhaust stroke, which makes me feel as though cam timing correct. I will have to sleep on it and try again tomorrow, like a fool I removed the electric starter so I have to kick this thing to death...

Cool it with the ether until you figure out why it isn't running.

[A-train]

Cool it with the ether until you figure out why it isn't running.

Agreed. Too much alcohol will dry out even the best of us...

[ashdricky]

Cool it with the ether until you figure out why it isn't running.

yes Sir.

I find a motor that has the cams retarded by about 45-50 degrees won't even pop a lick. If you are advanced too far it will certainly let you know with a bang. We just went thru this with a XS650 Yamaha, proper cam timing and 1 kick.

I guess I will need to look at the cams. Is it possible that even though I am still using the bottom end (crank, rods) from a 550 with the original cams/sprockets from the 550 that some kind of cam timing discrepancy would still occur? I am also using a manual cam chain tensioner if it matters. My understanding was that if I was off even one tooth eventually a valve would hang open and get jammed against a piston.

[Nessism]

To answer your question from earlier, yes, it is possible to have the cam timing 180 degrees out of phase and not bend the valves.

First thing I'd do is verify cam timing. Pull a plug from 1 or 4 and look inside while you turn over the engine and align the 1-4 T mark on the advancer unit. After you align the mark look inside the spark plug hole and make sure the piston is at the top of the stroke. Rotate the engine both ways and watch to see the piston drop, that way you know 1-4 is at TDC.

Now check the notches in the camshafts. If they are substantially off, you have a problem. There may be some mild misalignment, but that won't keep the engine from firing.

Of course you should check for spark and fuel in the float bowls too. One thing at a time. Best start with the mechanical side first is all, then move on.

[ashdricky]

To answer your question from earlier, yes, it is possible to have the cam timing 180 degrees out of phase and not bend the valves.

First thing I'd do is verify cam timing. Pull a plug from 1 or 4 and look inside while you turn over the engine and align the 1-4 T mark on the advancer unit. After you align the mark look inside the spark plug hole and make sure the piston is at the top of the stroke. Rotate the engine both ways and watch to see the piston drop, that way you know 1-4 is at TDC.

Now check the notches in the camshafts. If they are substantially off, you have a problem. There may be some mild misalignment, but that won't keep the engine from firing.

Of course you should check for spark and fuel in the float bowls too. One thing at a time. Best start with the mechanical side first is all, then move on.

Alright, I need to go turn a wrench for GE, but I will pull it apart when I get home from work.