81 SRX will not fire need HELP!!!

[messina1974]

I have an 81 and I cant seem to figure out why it will not start, I will list all that I have done trying to figure this out and see what you guys think. I have checked for spark and after replacing the CDI have obtained a good strong spark on both cylinders. I have installed a fuel shut off valve as it was flooding my cylinders last season. I tried to get it to fire by spraying starting fluid into the heads and also into the air box. I even dumped a lil fuel into each cylinder to make certain it was getting fuel. The sled will not fire, I did get ONE very loud back fire last nite when I was pulling the heck out of it. Other than the back fire I have not had any luck or indication that it wants to fire. Checked the compression on the cylinders one is at 110 the other is at 120 pounds. I feel this is probably a little low but figured its gotta be enough to get it to fire and run. Well I am stumped an was wondering what you all thought. Took pipes off to make sure nothing had gotten into them restricting air flow, and they were clean. Well at this point any ideas would be appreciated. THe only thing I can think of is that the timing has some how been thrown off since last winter, possibly sheared the key and maybe the flywheel has changed? Dont know and looking for help. Thanks guys MIKE.

[Bob Vehring]

If you try to start in a normal matter, do the plugs get wet? I would look to see if you are either getting too much gas (wet plugs) or no fuel ( dry plugs after trying to start).
I've never had a sled engine move the timing on me, A really hard back fire I guess could, but then you had the problem before it backfired. I would look at fuel delivery.
If you had a flooding issue, installing shut offs might have stopped it when there closed, but it didn't fix the problem of flooding in the first place. I would check that the needle and seat aren't sticking open.

[tyler440]

hmmm if the timing was off it should still fire and shoot flames out the carbs.... (i would think) ive sat here for 5 minutes and im still stumped.... brain isnt working right.... hate to leave you hangin but maybe someone else will jar my brain into action.... doesnt it have stock carbs or roundslides?

oh and btw welcome to vintage vmax.... we'll get your sled going just give it a bit so some of the other guys can give thier input....

[agfirecat]

yeah it def.sounds like a flooding issue mine did the same thing before i installed a shut off for the fuel . my base was full . scared the shit out of the wife when it backfired alsojust keep pulling it and swapping the plugs with dry ones and it should take off . also check to see if you dont have fuel going ito your base thru the pulse line wich would indicate your fuel pump has taken a dump.if these dont help then it could be your stator has moved . if ya need it i can get ya close on the timing marks to see if its out of wack.

[Vmax540]

'The sled will not fire, I did get ONE very loud back fire"]

We saw this with a member from here brought it to my house. After cleaning all connections, changing the CDI and stator plate the best we could get was a back fire every 3-4 pulls. We were stumped.... until someone (while we were pulling) wiggled the wire connections where the stator connects to the wiring harness and all of a sudden we had multible fires. Upon crimpimg these connections we had a running sled. When pushing these connections together the flexible plastic sheathes that cover the connections give the feeling that you have a good fit and in some cases the metal connections inside are still loose !

[Joe]

1) TIMING

Mark Left TDC and Right TDC with a sharpie on your clutch.
Put a timing light on the marks and see if you are getting both cylinders to fire just before TDC.
If the marks don't align, pull the flywheel and inspect the key.
If the spark is erratic, check for loose connections from the CDI connections toward the generator.
Wiggle the wires while you watch the continuity tester.
The connections to the stator tend to get loose and dirty.

2) FLOODING

Take both spark plugs out.
Turn off the ignition switch.
Put a socket on the clutch bolt head.
Spin the crank counter-clockwisewith a big drill motor or other electric motor.
If you get fuel out the spark plug holes, the bottom end is flooded therefore you will need to spin it over quite a while to get the fuel out even after you don't see any more fuel.
Turning off the fuel valves should reducing the incoming fuel.
Pulling the carb slides out will nearly eliminate fuel entering the engine unless it is getting in through the fuel pump pulse tube.
Disconnect the pulse tube if you suspect a ruptured diaphram.

[messina1974]

Thanks for the info I am not getting flooding into the case any longer as the plugs are damp after pulling over but not soaked. Prior to shut off valve I had flooding problems but went throught carbs. Now I shut off the fuel when storing as I have the rear end suspneded lil higher than when in use .Left the sled on suspension over nite with fuel on to make sure it was no longer flooding and that problem has been solved. I will get a big drill and spin motor over tonite to make sure no fuel in bottom. last time it flooded there was plenty of fuel in bottom as pipes were wet and fuel would shoot up with plugs out, and that is no longer the case. However I will pull the fuel line to the case tonite to see if that fixes anything. I thought that If I had spark then the connections must all be ok, Hence spark? am I wrong could I have a good spark and a bad connection at the same time leaving me with this problem? Also in regards to TDC which cylender is the one the would indicate TDC? if I bring up the piston which one would indicate or does it not matter. Thanks again for the posts.

[tyler440]

yeah that sled that vmax540 (chuck) referred to had good spark... but it still wouldnt fire right... that was an odd situation i still dont completely understand

[opsled]

The porting on those 81 440's has fairly radical. An engine with radical porting will not start well (if at all) with low compression and the comp #'s you stated are low (to the point of hard starting) for an 81. Your cylinders could be washed from fuel and your pipes could be full. The backfire you described (if out the exhaust) is a sign of fuel in the pipes. If you had the crankcase loaded with fuel it will take a lot of pulling to get it cleared and if the plugs are out while you are trying to clear out the fuel it will not pump the case clear of fuel.

I've had a few of these (440&540's) with flooded crankcases and it is not easy to get them cleared to run again.

Try pulling the pipes and dumping them to see if there is any fuel in them. Loaded pipes will not allow the cylinders to pump in a proper amount of air to get good compression. Leave the pipes and fuel off, squirt a little oil on the pistons through the plug holes (this will help with compression) then try to start it. The crankcase will clear faster if the pipes are not on and if your plugs are wet with the fuel off you still have fuel in the crankcase that is giving you trouble. The plugs should be dry every time you try to start it. If they keep getting wet you must keep drying them out and repeat the process untill it runs. Once it runs, clear it out good and put everthing back together.

You may have other issues as some are describing and possibly cylinder trouble with the low comp readings but intill you are sure it's not still loaded up on fuel you could be chasing your tail.

Good Luck, Phil (opsled)

[brjr540]

just my 2 cents here. i would try to add like a teaspoon full of #30 oil into each cylinder,pull it over slowly a couple times ,put fresh plugs in it then try to start. is the fuel fresh? i would be EXTREMLY careful using starting fluid.this could dry out the cylinder leading to much worse issues! good luck!

[messina1974]

Well guys here I am a year later and no fire. I have replaced the seals in the bottom half, looked like the one side was defineltly leaking. Replaced the pistons and rings installed properly arrow twards exhaust side and ring openings tward intake side, cleanded the carbs and set them. Plenty of real good blue spark, and not running??? I cannot figure out what this old girl needs to run. I am going to check ignition timing tonite as I have found a dial indicator, i am also going to check the compression this evening as well. Just wanted to put this back out there to see if there is something I am missing, or if it just doesnt want to be brought back to life. I am about ready to give up on it and put it for sale. I hate to sell it as I love this model and power it should have but just for the life of me cannot figure out what is happening. thanks guys mike

[Bob Vehring]

After some struggles, mine seems to be running good now. Problems late last year, begining of this year. Narroewed it down to one carb, changed every part 3 times, every part.. Every time I put a different carb on, it was good, went back no start with the original. Finally took all the parts, put them in a different carb body, all seems well, will let you know monday were leaving tomorrw.

[agfirecat]

is the cdi box the right one for the srx or could it be a 540 cdi on it?

[messina1974]

The CDI is the updated CDI 8R9 which if I understand it correctly was the CDI intially for the 82 srx 500 which ran fine couple yrs ago? Anyways have a little more information to mull over after last nights wrenching session. pulled and pulled and nothing, so I took the expansion chambers off and sure enough it started right up and ran till I turned the key off 10-15 seconds. no antifreeze in it and obviously the pipes were off so I shut it down. Re installed the pipes started filling with DEXCOOL (GM antifreeze not sure if thats a bad thing or not??) and no pop or fire. Took the pipes back off and again it fired up. (NOthing stuck in pipes) It appears if the back pressure of teh pipe is kililng the motor. I held the pipe close to jug and it started killing it, pulled it farther away or off and it picked right back up again. I have not been able to acquire a dial indicator to screw into plug hole yet to check ignition timing, but am still hunting. So bottom line is I guess its eithor the timing or the carbs? and was wondering if anyone had an Idea as to what could be happening here. Thanks so much for all your help regarding this problem. MIKE.