Outdoor Power Equipment and Small Engines - sick sounding b&s 15.5 ohv

Hello all
i have a 2002-03 sears 42 " cut tractor with a 15.5 ohv
the motor is running real funny it is backfiring and poping has lack of power it also some times hard to start it is like the motor had 600 lbs of compression but once i get started ti runs,
when i am mowing it starts bogging down so i stop mowing leaving the deck running and choke the motor it seams to pick up power a bit ,it don't sound right it sounds like a helicopter.

here is what i done i went and got some new gas mid grade
change the air filter
change fuel filter
change spark plug
i did this in the spring and i just did it again.

any have an idea i had one person say something about the valves are out of adj. i realy don't know and if it is the valves what are the settings.

Thanks for any help i can get with this matter.
Bob :confused::wall:

Ok, there are some checks you could do, but from your description and my experience, this sounds like a bad camshaft. I've had a run of them lately and the helicopter sound you described convinced me.

Remove the valve cover and look at the valve clearances. I'm betting one is really really loose, and when you adjust it, the valve will not open/close nearly as much as the other one. Take a look and see.

what are the specks on the valve clearances

help!!!!!!what are the specs on the valve clearances? what is the travlel on the push rods
both rocker arms both have slack.can any help or have advice
the motor model 31c707 type is 0230 code 030414za

i also notice that it is popping in the carb

Here is a post from 31YTech that should do ya for diagnostic purposed at the very least. http://forum.doityourself.com/1612949-post3.html

As far as the travel, I don't imagine both lobes would have problems although it is possible. cheese will have to fill in more there.
One thing you can look for however, is to see if one travels noticeably more than the other.
Popping from the carb can be a symptom of valves not opening properly or far enough.

ok i set the valves and it starts great but it sill pops in the carb. when i increase the throttle it pops then kinda stops poping

can i put a video in this page anyone know.

upload the video to youtube then post the URL.

ok i set the valves and it starts great but it sill pops in the carb. when i increase the throttle it pops then kinda stops poping

can i put a video in this page anyone know.

Well it could be two fold, your valves may have well been out of adjustment, and you could still have a cam issue, or other valve train issues or even carb problems.

How does the spark plug look after running it?

well the video does not have sound.
i was looking @ the motor and when the motor is idleing it runs fine when i give some gas going to full throttle it pops 6 times then it smothout and still sounds like helicopter .Beer 4U2Beer 4U2Beer 4U2Beer 4U2Beer 4U2

the plug is new and it look cleanBeer 4U2:alarm::cool:

spark plug?
Will it handle a load?

Sounding more n more to me like cheese is on the mark.

If the motor is running in full throttle and I engage the blades, it starts popping. If I move the throtte to slow, then engage the blades, it will run almost full before it starts popping, but in full, it pops.

you could still have a cam issue, or other valve train issues or even carb problems.

BFH just may be on to something here since the valves are now adjusted properly.

Bob,

Crank this baby up then throttle it where it starts popping and slowly apply the choke and see if the popping goes away.

If it does, Rip the carb off and tear it down, Give it a good cleaning with carb & choke spray cleaner shooting through all ports-passages and jets.

ok here we go if i run it to full pops afew time smooth out then starts popping choke it and stop popping then boggs down if i just close a little it quits popping

i had a guy give me an 18.5 hp ohv model 31p777 type 0296e1 code 031218zp

will the sump pate,cam and lifters work on my motor
model 31c707 type is 0230 code 030414za

why i was asking about the sump plate the one that was given to me has an oil pump and filter, will it work on the my motor. let me know.

BFH just may be on to something here since the valves are now adjusted properly.

Bob,

Crank this baby up then throttle it where it starts popping and slowly apply the choke and see if the popping goes away.

If it does, Rip the carb off and tear it down, Give it a good cleaning with carb & choke spray cleaner shooting through all ports-passages and jets.

do i need to take the mixture adjuster out and if do what is the setting on it

You have a PM on the sump/pan issue.....

Screw the adjuster in until it's LIGHTLY seated counting the turns as you go, Then screw it back out for cleaning then screw it back in until LIGHTLY seated and back it out the number of turns you counted.

This will put it back at a good starting point which can be fine tuned from there once the engine is running and warmed up (with the air filter in place).


Good Luck

I am still putting my money on a bad camshaft. Exact symptom description. When you adjusted the valves, did you not check the movement of the valves and compare one to the other? Measure how far one valve opens, then the other.

ok i will have to get my dial caliper out

A ruler should suffice. If the cam is worn enough to cause a problem, the difference in travel should be obvious. Your talking about an inch or two...give r take....:o

well i chk the travel between the intake and exhaust vales the intake 2000th more than the exhaust:coffee::coffee:

well i took the carb off clean it and put a kit in it still the sameBeer 4U2Beer 4U2x 1000,000,000,000.00

if the camshaft is bad/worn out, there maybe shaveings in the oil. is there any silverish sludge/bits on the bottom of the dipstick?

considering you didn`t already change the oil.

well give cheese a big big cup of coffee i pulled the motor down the exhaust lobe is gone completely gone what cause this to happen i had the carb to flood the motor and i change the oil as soon it happened i put fresh oil in it started it up ran it for a min or two then i change it again :coffee::coffee::coffee:

what can i use to clean the inside of the motor out and hopefuly i wont have to take the motor down to the bare block.


the orgnal cam has a wing on the bottom side of the gear
i think it is the compression release

the new cam dose not have it will this make any differance
please let me know

Well,

I must admit, I was doubtful of the cam only because I'm yet to run across one being wiped out.

Good call Mr. Cheese ! http://www.xtremesystems.org/forums/images/smilies/thumbsup.gif


Bob,

Look at it this way, Least now you know the carb is clean and will perform properly for a while.....:thumbup:


You could use automotive brake cleaner and where did you get the new cam ? It needs to have a compression release on it or you will be back to square one trying to start it.

i would strip the motor down as much as i could.
reason being that any little particals will wear at other parts
as well as a cam shaft.
especially main bearings,wrist pins. if one of them goes then your really in for a rebuild.

a paint brush, air compressor blow nozzle,and mineral spirits. i use press wash (the stuff i use to take ink off my press rollers)

gunk engine cleaner works good to. you`ll want to clean the outside first to avoid crumbs and stuff falling inside as you disassemble so you have less to clean out.

the farther you go in cleaning and taking it down to the bare block the more likely the odds you`ll have cleaned all the crime out and will last you longer without premature wear to any other parts.

You need compression release. Don't install a cam without it. The new cam kit is around $90 and comes with new lifters. If you use the old lifters, they will ruin the new cam.

I only knew what was wrong because I have run into several engines with this problem. When you get one in the shop, you will understand the "helicopter sound".

does anybody have the torks Specifications

For what? You shouldn't need to remove the rod bolts or head bolts (the ones that are more torque-critical).

well !!!!! i stripped down to just a block. when i cleaned the piston a lot of silverish stuff came out. i feel that i needed to take down to block and make sure it was all clean out. i now can be sure that it is right. that is why i asked what type of lube to use to put the motor back together do you think i need to take the head into a shop and have the vales done???
let me know
that is why i need the torque spec. and torque sequence

The rod bolts are 150 inch lbs, the head bolts are 220 inch lbs, tighten them in a crisscross-star pattern.

You can pick up engine assembly lube at an auto parts store. I used to use vaseline on automatic transmissions when I was in the automotive field because it is petroleum based and harmlessly melts away into the oil as soon as it warms up. I now use it on cam lobes and bearing surfaces and seals for the same reasons.

I removed the reference to a link that apparently can't be used to look up a service manual.

Hi cheese
you said enter your numbers here i didn't see a link to enter my #'s:coffee:

I edited the post for you.

ok the that about flywheel

65 foot pounds on the flywheel bolt.

still working on the motor