Craftsman Mower Problem: Runs fine until blades are engaged.

I have a craftsman 18HP; Twin Cylinder; 42" Deck, 5 Speed Transaxle. (Model # 917.258492). I was given the mower by my neighbor, he told me it had a few issues. New set of plugs, starter and a fuel line, and it has work perfectly for two seasons, until last week. All of a sudden, i went out to start the mower and it fired right up, idled fine, put it in gear and it barely moved. So my first assumption was the drive belt..it was cracked, and stretched, so I figured it was a likely choice. After replacing the belt it did seems to have help as the mower now drive great, but once I lower the mowing deck and engage the blades the power level of the mower with in gear and blades engaged is almost zero. If I engage the clutch; disengage the blades the mower returns to normal operating RPMS; also if I raise the deck it moves a bit faster and mows a tad bit, but ultimately starts to stall out. I am sure I am over looking something fairly simple, but for the life of me, I cannot figure out what. Both blades spin freely under the deck when mower is off as well. Fuel Starvation?; Safety Switch? I have to jump the solenoid to start the mower as the ignition switch seems to be faulty, but it does turn the mower off when switched to off position..could this cause this type of problem?...:confused2::confused2::confused2::confused2:
Any suggestions would be greatly appreciated.

Thanks in advance for help
Shadetree_Dechanic

Hi
This all sounds a bit strange?.
I don稚 know this machine does it have a clutch on the end of the engine crankshaft with two drive belts on (one for the trans and one for the deck)?

Hi Again

917.258492 Craftsman 18 HP 42 Inch Mower 5 Speed Lawn Tractor

Is this your machine?

Yep. That is it.

OK
The link on the last post was to a parts list of your machine it might come in handy.
This is going to be a process of elimination.
If it starts and runs ok then you can rule out fuel, ignition and safety switches

For you description it sounds as if the engine is coming under too high a load.
Presuming you are running the engine at full throttle when engaging the blades then it can only be a number of things.

1. Is the new drive belt at the correct tension if it is too tight it will drag and then with the extra load of the blades it could be enough to pull the engine down and worse still if it is to tight the loads put on the belt during use can bend the crankshaft (I know the drive belt is not connected to the cutter deck but trust me I have seen it happen so many times).
2. The idler pulleys on the cutter deck are they free, turning and inline.
3. You say the blades turn to test how easy they turn drop the deck drive belt off the engine pulley and pull the belt round by hand you will soon see if there is anything dragging on the deck.
4. There is probably a little brake system on top of one of the blade pulleys (try the left hand side first) check that it is not stuck in it should automatically disengage when you lower the deck into work and engage when you lift the deck up in to the park / transport position it is designed to stop the blades from spinning for too long when coming out of work they can and do rust up.
5. I am sure you have checked this but do the blade turn all the way round. If they stop or get stiff part way round it could be a bent shaft or a bearing on its way out or even just a lump of last years grass stuck to the deck and gone rock hard.

Good luck and let me know how you get on.

@webuyanymower.com;
First of all; thank you for your response. I will go down the list this afternoon, and give you an update this evening.

:confused2:Shadetree_Dechanic:confused2:

Are you sure you put the belt on right ? Engaging the blades and bogging down I would assume you went the wrong way around a tensioner pulley . I see this in she shop where the customer loses brakes because the rear is engaged all the time .

@SONOFADOCKER;
Thank you for your response, I did double check to make sure the belt was on the right side of the tensioner pulley, and it was ok.

@webuyanymower.com; I went through the the list you provided, and everything seemed to to work as intended. Although it did give me a different perspective as I was going threw the list, none of the items seemed to fixed the problem. I did however leave out on essential part of the the equation....my "little helper"; while I was putting the new drive belt on last weekend, my daughter was sitting on the mower "Helping". As I was checking the pulleys etc, I noticed the deck was sitting very..very low; well my lovely 2 year old had turned the adjustment knob to the lowest setting, and removed the knob, thus when I was lowering the deck..it was burying the blades in the already high and thick grass. So a lesson learned..Occam's razor-"the simplest explanation is most likely the correct one." I was able to correct to problem, and get the mower working correctly.

I do want to thank everyone for their suggestions, which allowed me to discover the problem. I am sure I will have more "issues" in need of answers, as well as being able to hopefully help others.

Again thank you all for your time and suggestions
Shadetree_Dechanic:thumbsup:

Hooray for little helpers?well done :thumbsup:

I have a 2082 20 hp twin kohler on my cub cadet . put new oil seal on front shaft an now when you engage the blades it drags the motor down . could it be a bad clutch on it ? need help or an answer on this . thank you