Hello All,

New to the forums and hope to learn from all the pros here.

Heres my deal, Bought a 2003 predator 90 for my daughter. Was a nationally raced quad with quite a few hop ups. I made the transition back to stock and sold off all the parts. Added an 18mm mikuni and love it. Everything is back together and it runs fantastic. Nice and smooth, starts on first kick, etc.

But....now that the stock exhaust is back on i can hear a knocking in the motor. At first sounded like the clutches. after rebuilding both (new rollers, sheaves, springs, belt) it was still there. It now sounds like it is on the right side of the motor. It is very noticeable at idle, gets higher with rpms and becomes less noticeable while moving. My goal was to make the quad as quiet as possible for her and this is the loudest thing on the quad!

Is this normal? Crank bearings? Rod bearings? I was told it has recent ring job. I have also been reading polaris quads are noisy. Am i making a big deal out of nothing? Like i said it runs out just fine but noisy sitting at idle.

Any help is GREATLY appreciated, thank you!

 

Welcome to the forum! I think your second sentence "was a nationally raced quad with quite a few hop ups" may have answered a lot of questions. NO this isn't normal and shouldn't be loud at least new out of the crate they weren't! Could be rod bearing,crank bearing noise as you mentioned?Plus I wouldn't take any ones word on the ring job either! Not that hard to tear the head and cylinder down and check it out! Good luck OPT

 

Thanks for the response. Believe me i dont trust anybody's word now days, especially this guy. I felt good about the ring job because compression feels great. Havent tested it but i can feel its pretty significant from kickstarter and clutch. So when these little things are at idle you should not here any rattles or knocking? This sux, how bad is a rebuild? This guy really took me on this quad. I started to feel better after i got some money back on the parts but now I am in the dumps again

 

Best to get a manual as the whole engine and clutch assy has to be taken out if the bottom end is bad. You can tell if rod or bearings are bad when you pull the cylinder. If rod has ANY up and down play,will have to be replaced(side to side ok),plus you can usually feel crank bearings as you turn rod.Complete crank and rod assys are available aftermarket along with piston and cylinder kits! Good luck OPT

 

This helps, thanks again. 1 more if you dont mind, by ''up and down'' you mean ''in and out'' of the case? so if i pull off jug and pull and push on rod there should be no slop?

 

No in and out play on the rod! OPT

 

what are my options OPT? Is there ANY possibility it could be something else? It runs awesome as it is, do we stop riding it or wait for more signs before replacing anything? I found a new crank/rod combo for under $100 new, but dont want to spend any more money if i dont have to.

Can i wiggle the stator or clutch to test crank bearings and narrow it down to rod bearing? I pulled the spark plug last night and noticed it was gapped very tight. Would the piston hit the tip of spark plug if bearings are failing and what should normal spark plug gap be?

Please excuse my lack of knowledge and many questions. I have spent countless hours of searching for answers and your the best and all i have right now! God bless

 

You can try to wiggle the flywheel to see if you feel play in the crank bearings,(may or may not be able to feel any movement)but whether its the crank bearings, lower rod bearing,slack in the upper rod piston pin and piston,the engine will have to be torn down unless its just a worn piston only making the noise!!! I'm just going by your description of the noise! Don't know what else it could be unless you can trace the noise to the clutch area??. If the piston hit the plug you would know it in a hurry! It wouldn't run! Just remove the cylinder and head and you can check the rod and piston and possibly feel any problems in the crank bearings! (Even if its not the problem it only takes a new head gasket and base gasket to reassemble!) If unsure just let someone experienced listen! They shouldn't charge anything for this! I checked many machines on pickups and trailers at no charge and let the owners decide!! OPT

 

Thanks OPT. I have narrowed it down to the lower rod bearing. I was able to get to the stator and found no wiggle at all. But while rotating and rocking the crank back and forth i could hear the knocking. it only did it when the rod was at a certain point. I took intake off and stuck my fingers in and pushed on the bottom of the rod while i wiggled crank. with the added pressure the rod had no slop and did not clank.

So, for future amateur mechanics, it is possible to feel the rod bearings without removing the head (if your situation matched mine)

If I buy a new crank/rod, would you recommend i do the upper rod bearings as well? anything else i should replace while in there as ''preventative maintenance''? Dont want to do this twice.

You have been a tremendous help, and it didnt cost me a dime!! Thanks!

 

Always replace the upper rod bearing and pin when you install a new crank assembly! Plus don't forget to order the crank seals also. Good luck OPT