What are the symptom of an engine that will blow??!! long story

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fortress

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(UPDATE PICS) What are the symptom of an engine that will blow?

Hi guys! well, i'm very discouraged with my sled

well, if you remember me, i did post alots of question in the last 2 years about my sled problem

the problem is simple, no power when i squeeze the throttle to the handle bar,,, the rpm would rev to 8200 and drop to 7800 7900 and the engine act like if he would run on two cylinder or if a carburator was not fonctionning correctly.. It run idle very well, start very well ...

Before you tell me to check all the simple thing, i will tell you what have been done on this sled to solve the problem


Checked the wire under the engine
Checked all the wire that goes from the stator to the CDI
Tried a new CDI BOX
NEW valves and they have been adjusted
Powervalves motor is ok
I did test the sled with the Valves open manually
both clutch serviced
bearing of the chaincaise are new
I did try the sled with light disconnected, handwarmer disconnected
The crankshaft have been checked by a shop

I was not sure last winter about my compression but when we did open the engine, my friend did check the measurement between the piston and the cylinder and it was in the norm of the manual.. but, we did take the compression with a gage after that.. about 125 124 but we had to crank like 8 shot or more to reach that compression. We did know at this time if it was normal or not

Ok, this summer, i did change the stator, pull the proaction system out of the sled and change all the bearing, put grease etc etc...

NOW, yesterday, i start the sled, let run idle,, after 5 min, push the throttle to the handlebar, act bogus and i did blow a spark plug.. I did put new spark plug

This morning, take the sled to the trail,, IT WORKED GREAT for about 15 min.. the power was there.. after it acted bogus again.. I did really feel the lost of power.. its like if i was towing something.. So, we did trailride 1 hour and i did make several stop and go testing and the sled acted bogus

NOW, what happened at last, after a stop and go test, i did blow a sparkplug

the sparkplug on the magneto side was affected.. i dont know the terms but the little "tongue" was pushed toward the electrode.. So, i think that the piston his destroyed right?

My question is,, my problem, from the beginning, was an engine problem or it could be just another coincidence that my engine did blow this morning and could still have the same bogus sled after changing the piston?? What's the symptom of a bad compression engine.. remember that the sled run bad since 2 winters.. I would think that a bad engine will not run 2 winters before blowing??

By the way, the only thing i did not check , is the interior of my carb,, but humm,, what carburator problem could cause this?? if the sled run fine in idle mode and cruising mode
sorry for my english and the longue story
 
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when was the last time you cleaned your carbs?
did you diconect the TORS? ( 2 wires comming from the carbs disconect them and conect together) my gues was the problem all along

Have you pulled your head or looked in with a bend a light to see if your rings went, my guess is your plug was bumped before install.

check the simple things first. good luck
 
Concept Carbon said:
when was the last time you cleaned your carbs?
did you diconect the TORS? ( 2 wires comming from the carbs disconect them and conect together) my gues was the problem all along

Have you pulled your head or looked in with a bend a light to see if your rings went, my guess is your plug was bumped before install.

check the simple things first. good luck
Click to expand...

well. if the spark plug were bumped, it would not have worked for 1 hour

and yes, i did try to disconnect the TORS.. i did make all the test possible

i really don't remember when was the last time but why the sled would work for 15 min if the carb have something to do with this. i would thing that if the carb were in trouble, it would not work
 
when you said the plug was "bumped" and in your first post you had said that the tongue was pushed towards the electrode did it look like it had been physically hit by something?? look down into that cylinder and inspect the piston to double check that theres no damage on it
 
dirty carbs or water in the gas can cause some of the simptons u described. some water or a pice of dirt floating around in there geting sucked into the jet every once in a while and then making its way out could cause it. 90% of the time if ur motor is having problems and crank phase and compression checks out ok its mostlikely the carbs or gas. plus its the cheepest and easyest thing to check. i work at a sled shop and i know there can be alot of problems that have the same symptons but its a matter of elimination. best order ive found for sleds or any other thing i work on all the time like snowblowers, chainsaws, lawnmores that wont run or run crapy. first check spark and spark plugs, using a spark tester is the best way motor can still run and u can see if its sparking or not. if spark check gas tank with a light for water. if u dont see any seperation in the bottom of the tank and carbs arent the easyest to get off check compression. if its over 100 usualy the motor should run. then if compression checks out and its more then a single cylinder check to make sure the crank isnt out of phaze(twisted) with a 3 cylinder is easy, take the plugs out but center at TDC and use a screwdriver to check the depth of the other 2 they should within a 1/4 inch of eachother if not the same. if thats fine check the carbs for dirt and having right jetting, dump the gas in the bowl out on a cement floor if u can see seperation its water. also check for any green , white or brownish build up in the bowls. if there is its prolly every ware in the carb. check the jets for being cloged a pice of wire some carb cleaner and a air compressor with a blower can save most any jet. also checking fule or air screws and blowing out any passages are key. after that if u still have the same problem then id check electrical. if electrical checks out then its time to pull the motor apart and check bearings, gaskets, rings, pistons and cylinders. oh if it has PVs check thoes some where around the same as the carbs. if u go threw that order and still cant figure it out its prolly somthing realy stupid or major and ull be kicking ur slef in the *** either way
 
Skidooslayer687 said:
when you said the plug was "bumped" and in your first post you had said that the tongue was pushed towards the electrode did it look like it had been physically hit by something?? look down into that cylinder and inspect the piston to double check that theres no damage on it
Click to expand...

yes, it look like physically hit.. the spark plug were black and the other were brown


i tried to look down with a light but i see nothing.. i will bring the sled to my friend this week to open the engine but i'm curious to know to symptom of an engine that way blow.. if it would act like mine
 
terret725 said:
dirty carbs or water in the gas can cause some of the simptons u described. some water or a pice of dirt floating around in there geting sucked into the jet every once in a while and then making its way out could cause it. 90% of the time if ur motor is having problems and crank phase and compression checks out ok its mostlikely the carbs or gas. plus its the cheepest and easyest thing to check. i work at a sled shop and i know there can be alot of problems that have the same symptons but its a matter of elimination. best order ive found for sleds or any other thing i work on all the time like snowblowers, chainsaws, lawnmores that wont run or run crapy. first check spark and spark plugs, using a spark tester is the best way motor can still run and u can see if its sparking or not. if spark check gas tank with a light for water. if u dont see any seperation in the bottom of the tank and carbs arent the easyest to get off check compression. if its over 100 usualy the motor should run. then if compression checks out and its more then a single cylinder check to make sure the crank isnt out of phaze(twisted) with a 3 cylinder is easy, take the plugs out but center at TDC and use a screwdriver to check the depth of the other 2 they should within a 1/4 inch of eachother if not the same. if thats fine check the carbs for dirt and having right jetting, dump the gas in the bowl out on a cement floor if u can see seperation its water. also check for any green , white or brownish build up in the bowls. if there is its prolly every ware in the carb. check the jets for being cloged a pice of wire some carb cleaner and a air compressor with a blower can save most any jet. also checking fule or air screws and blowing out any passages are key. after that if u still have the same problem then id check electrical. if electrical checks out then its time to pull the motor apart and check bearings, gaskets, rings, pistons and cylinders. oh if it has PVs check thoes some where around the same as the carbs. if u go threw that order and still cant figure it out its prolly somthing realy stupid or major and ull be kicking ur slef in the *** either way
Click to expand...

hi!! like i said, the engine have been open last spring and the crankshaft have been checked, compression too.. So, we did eliminate the possibility of an engine issue but like i said, i was not sure if the fact that we had to crank the like 10 shot to reach 125 on the cylinder is normal

The last thing i need to check is the carb.. its really the only thing that havent been re-checked... i''ll do what you said

thx for your help guys
 
if it looks like it physically something physically hit the plug then there will be a mark on the top of this piston, it might be hard to find though without having the head off just so ya can see a lot better, the engine still rolls over nice and everything when the plugs are out?? do as terret said and check to see if all the pistons come up the same amount... i've seen it at work a few times now where a tractor would come in and one cylinder would be bad because the rod actually stretched, now i realize that its a big diesel engine however doing that simple check will eliminate that aspect of it.
 
alot of times a motor will run the best it ever has right befor it blows. but this is usualy with a motor that doesnt have a ton of time on it. most of the times the reason they blow is the carbs get dirty and lean out and they make more heat and more power then they can handel. one thing that cuses it to just go with some sign is water in the gas. itll run like crap then ull burn down cause one cylinder isnt geting any gas or oil so it heats up to much and when it does get some it burns down
 
If the piston hit the plug it could be a bad bearing and the engine would have a knock. Place an extra washer on the plug and turn the engine over. That may prevent the piston from hitting the plug, and you should be able to hear the knock if a bearing is gone. Possibly the head was shaved creating a clearence problem?? Check the threads were the plug goes in. The problem one could be going deeper than the others. Also if the carbs have not been cleaned, that is a must do like others have suggested.
 
Yes, clean the carbs as others have already suggested. Also check to see if the airbox has been gutted [I don't think so as you say the plugs are brown] and check to see what jetting is in the carbs, perhaps someone had played with it before you bought it.
When you took the plug out did you notice any small metalic filings on it?
 
justaviper said:
If the piston hit the plug it could be a bad bearing and the engine would have a knock. Place an extra washer on the plug and turn the engine over. That may prevent the piston from hitting the plug, and you should be able to hear the knock if a bearing is gone. Possibly the head was shaved creating a clearence problem?? Check the threads were the plug goes in. The problem one could be going deeper than the others. Also if the carbs have not been cleaned, that is a must do like others have suggested.
Click to expand...


well i dont think its a bearing cuz when the spark plug did blow, yesterday, i did put another plug and returned to the car,, but the sled wasnt able to idle right but i was still able to push the throttle and have power
maybe the other plug were damaged but they still make fire..
 
Equalizer said:
Yes, clean the carbs as others have already suggested. Also check to see if the airbox has been gutted [I don't think so as you say the plugs are brown] and check to see what jetting is in the carbs, perhaps someone had played with it before you bought it.
When you took the plug out did you notice any small metalic filings on it?
Click to expand...
well, i did just notice that something did hit the plug cuz the little "tongue" had some scracth on it


so, imagine that i had one cylinder that the compression wasnt good enough,, does the sled would act like that?? when i push the throttle??

the sound of the engine chance when i push the throttle to the handlebare and reach 8000 rpm.. like if he want to die or... difficult to explain lol
 
I would get yourself a small maglite flashlite and or the best thing is to use the fiber optic attachment and stick this down in the sparkplug hole in question with the piston down about halfway from top dead center you can view the entire piston top and see if you have small indentations on the exhaust edge of the pistons. This is going to be looking for detonation, this can close the gap on sparkplugs, it can beat the rod bearings enough to ruin them and let the rod begin to destroy things or it could very well be the possibilty of a crank pahse problem, this will definitly show up as a low rpm problem, do some checking and post results. If you do pull the head off post some pics of the cylinder in question.
 
how about flushing the fuel tank and changing filter in the tank? found alot of everything in a used sled i bought started the fuel system over from scratch and cleaned the carbs and have been raging ever since
 
fuel pump tired and cant keep up? burn the fuel in the bowls and the fuel pump is behind and cant keep up how bout the reeds? are they cracked or anything
 
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