engine vibrating on one side and knocking

99_Sportsman335Olive · #1 (**permalink**) 06-16-2011, 07:26 PM

Ok, for the life of me I can't tell what my next step should be!! Before I spend too much time and money either tearing down the engine or the primary maybe someone can help me out a bit more here!!

Here's what I got... I'll be as brief as possible

99 Polaris 335 I picked up used last fall for $900. Started and idled good but underpowered and would only move in low range. Got it home and first thing I did was pull apart the carb and found that the diaphram on the slider wasn't sealed properly(top of carb) Fixed the diaphram and cleaned up the carb and it ran great. Run Sea Foam in every tank since. Installed new plug and have checked it a couple of times and coloration shows good clean burn. Changed all the fluids and put on a new belt and cleaned up the sheaves as the other one was slipping a bit because of the underpowered condition and the previous owner trying to drive it in high. The previous owner also said he replaced the primary and I see a date code stamped 2009 on it. Had to rebuild the secondary as the buttons were totaly worn out! Just finished adjusting the valves last weekend, they were at maybe .008-.009" so set to .006" as per manual and no noticable difference in knock.... seems to have good power for a 335, even with the 2" larger mud tires than stk!

Problem is that I have a knocking that is VERY noticable at idle almost like a diesel. In neutral as you slowly rev it a bit at a time the knocking increases with the RPM at first then seems to go away but at the same time the body of the quad gets a vibration throughout. This is probably happening AROUND 2500 on through 3500RPM?? (no tach). Bring the RPMs up higher and the vibration is gone and the engine keeps making power to WOT and sounds good. The vibration and the knocking is there both in neutral or in gear

Anyone have a direction for me???

polman500 · #2 (**permalink**) 06-17-2011, 04:34 AM

Could be piston slap. Have you checked the compression? How dirty was the engine oil when you changed it? Also check the crank case vent into the air box to see how much blowby you're getting.

99_Sportsman335Olive · #3 (**permalink**) 06-17-2011, 05:17 AM

Good point,

The oil was pretty bad when I first changed it after purchase....

There is quite a bit of pressure coming from the crankcase vent line.

I thought that you couldn't do a a compression check on the engine because of the "decompressor" or whatever it's called that drops compression when starting or am I just way off on this??

jstoppok · #4 (**permalink**) 06-17-2011, 05:47 AM

Quote:

Originally Posted by 99_Sportsman335Olive

Good point,

The oil was pretty bad when I first changed it after purchase....

There is quite a bit of pressure coming from the crankcase vent line.

I thought that you couldn't do a a compression check on the engine because of the "decompressor" or whatever it's called that drops compression when starting or am I just way off on this??

It sounds like a loose piston to me too. Maybe there's a way to temporarily disable the "decompressor" while you do the compression test.

99_Sportsman335Olive · #5 (**permalink**) 06-17-2011, 06:32 AM

So in the thought of a bad piston while I'm trying to figure a way to do a compresson test....

I have googled and check most of the parts suppliers online for a piston kit for this 335 and have come up completely empty!! Not even one on ebay!

Anyone have places I could try???

ppolaris1010 · #6 (**permalink**) 06-18-2011, 07:38 AM

try babbitsonline they have them.i have a 99 500 and it had a similar problem but knocked under a load more so than idle and after tearing the engine down found it was the crank walking back and forth on the bearings.you could grab the flywheel and move it back and forth almost a quarter inch.put new bearings in it and some shaft saver goop i got from a bearing supplier to lock the crank the the bearing races because the crank was worn i could slide the bearings off by hand and no more knock.your clutch will also make a knocking noise if its worn best way to check it is take the clutch off and run it see if the noise goes away if the clutch is out of balance from being worn it will cause a vibration also .there is also shims on the crank balance shaft and oil pump if there worn or out of wack it will also knock and vibrate excessivly.listen to the engine really closely with the clutch off and try to pin point where its the loudest before wasting money on a piston that may not fix it.your engine is pretty much the same as the 500 block crank and balance shaft wise

99_Sportsman335Olive · #7 (**permalink**) 06-18-2011, 08:05 AM

Thanks ppolaris1010! That's some good info!

I did have the manual pull start cover off and pulled back and forth on the flywheel. Had a little play but didn't seem excessive. I also started the quard with the starter gear removed to make sure it wasn't that rattling around.
As close as I can tell the knock seems louder on the right side of the engine. The knocking sounds most concentrated right at the cooling fins on the side of the head or just slightly below but not any lower say at crank area.
With the clutch cover off the knock is not any louder and as daring as I am getting close to the spinning primary it doesn't seem to be there....
I just changed the oil from last fall and it seems like after i put fresh oil in and give it a 10-20min run the knocking seems slightly more faint.

I do not have a clutch puller otherwise that would be my next step.... as mentioned in the first post previous owner said he changed it and it does say 2009 date code... without removing what can I see/check for wear or loose parts???

I'll check out babbits! Thanks!

Russ C · #8 (**permalink**) 06-18-2011, 01:35 PM

go to harbor freight and buy a cheap stethescope, they work well form listening to things for rattles ect

ppolaris1010 · #9 (**permalink**) 06-20-2011, 03:34 PM

check the bolts that hold the weights on and check the weights take the bolt off and the weight out you have to pull the cover of the clutch off to do this and slide the weight back on the bolt shaft while its out and see how much slop there is shouldn't be any.new clutches dont come with weights or the spring so if they were worn out it will wear your new clutch out fairly quickly because the weights will not be in sink and pushing the clutch off center wearing the bushings out faster.also use a polaris belt dont use after market and if the belt was slipping alittle i would put a new spring in it they loose there stiffness over time and its another indication your clutch could be binding or your secondary is wore out.the bogging engine could have something to do with it to.but is something to check