Top end rattle help

[honda200x1987]

I have a 350 Rancher with a new crank, new NICHE cylinder with new piston/,pin and rings,Tight timing chain.. I can't figure out what this rattle is.. the valves are tight... I'm leaning towards the Cheap Niche cylinder that has play but it's brand new maybe piston slap?

[shortline10]

Are you positive it’s not timing chain slop ?
Only way to tell is by pulling the back cover off .
Also the auto timing chain tensioners do fail .
I’ve installed a lot or those Niche rancher cylinders with no issues at all , definitely don’t use their pistons though .

[honda200x1987]

https://youtu.be/aEpXJPvZgI8

[honda200x1987]

I split the cases and has a New timing chain, it was tight when I assembled it

[Shep1970]

I may be way off base here, not sure what yr your rancher is but didn't the earlier models have a decompression lever system? If yours does it sounds to me like the decomp part in the head is clacking against a rocker. Your cable too tight? If you have one. Thats all i got.... good luck

shep

[honda200x1987]

I may be way off base here, not sure what yr your rancher is but didn't the earlier models have a decompression lever system? If yours does it sounds to me like the decomp part in the head is clacking against a rocker. Your cable too tight? If you have one. Thats all i got.... good luck

shep thanks for your reply, unfortunately this model does not have a compression release

[honda200x1987]

It really has me stumped and it's the same sound before I rebuilt it! What's strange is I replaced the old crankshaft because the rod had wrist pin play so I was certain that was the issue.

[Shep1970]

Lurking around the web- it seems some 350 ranchers have valve seat issues- again i have no idea if this is your problem but over the last hour i must of read 10 different posts about loose valve seats or failing altogether. I'd imagine though if u had it apart you'd of noticed something. Just an example-
https://www.hondaatvforums.net/threads/350-cylinder-head-dropped-valve-seat.99594/

shep

[honda200x1987]

Think I have an idea, it could be worn rocker arm shaft

[shortline10]

The cam followers / caps , push rods and rockers when worn can make that rattle noise . Basically their excessively loose during the rotation of the camshaft even though their at spec at top dead center . I’ve seen the followers cuped were the camshaft pushes on them as well .

Another thing to check is the tappet adjustment screw , sometimes they get worn on an angle were they touch the valve and make it impossible to get a good adjustment .

The camshaft does have a decompression mechanism built into it and if stuck open or worn can cause the that rattle as well .

[honda200x1987]

It wasn't the rockers, it must be a defective NICHE cylinder/piston kit. First time I used this after market brand, I've bought others without any issues. I will tear it back down Sunday

[shortline10]

I’ve run into this several times with the 350/450 models
It usually ends up bending a valve or loss of compression .



Lurking around the web- it seems some 350 ranchers have valve seat issues- again i have no idea if this is your problem but over the last hour i must of read 10 different posts about loose valve seats or failing altogether. I'd imagine though if u had it apart you'd of noticed something. Just an example-
https://www.hondaatvforums.net/threads/350-cylinder-head-dropped-valve-seat.99594/

shep

[honda200x1987]

Figured it out.. it was DEFINITELY the NICHE cylinder kit.. the bores are out of spec. It sounded fine at Idle but when I give it gas it would rattle. Clearance between the cylinder wall and the piston was .005 . The seller on eBay sent me another and it sounded exactly the same, similar clearance also. So I installed a different brand I normally use and it sounded perfect.. nothing better than OEM but I'm staying away from this NICHE brand!

[shortline10]

So do you know if the bore was to big or the piston was made to small ?
Like I said earlier I use their cylinders all the time but never use their pistons .
I have two niche rancher 350 cylinders in stock , I use prox pistons with them and never had that problem .

[honda200x1987]

So do you know if the bore was to big or the piston was made to small ?
Like I said earlier I use their cylinders all the time but never use their pistons .
I have two niche rancher 350 cylinders in stock , I use prox pistons with them and never had that problem .

Yup.. I used a different aftermarket piston in the NICHE cylinder and it sounds great. It's the pistons that comes with the NICHE kits they sell on eBay.... So the cylinders are fine, the pistons have too much clearance

[big specht]

Glade you figured it out and posted your findings so many of these threads never give a ending.

[ATC200X4716]

Just a little feedback on pistons and cylinders. I've been boring and honing bike cylinders for 25 years so I've seen it all. The Niche brand are crap for quality control. There isn't any. I set them up and measure them on a sunnen gage which reads down to .0001 inch against a calibrated standard and new out of the box their piston cylinder kits are quite loose. Some are loose by .003" to .006 which is near double the clearance for a cast piston. If you buy their oversize piston and fit it to your cylinder by a reputable machine shop, they work ok. I strongly recommend Wiseco pistons as they are forged blanks. Much stronger, with quality control. OEM pistons or Wiseco pistons are the only ones I will size the cylinder without the piston in hand and the clearance always comes out spot on. Those Niche pistons are $3 pistons they overcharge for. You get a better quality job buying a OEM or Wiseco piston and putting it in your OEM resized cylinder. Break in the piston properly for several hours of easy riding, and change the oil. Use good oil. Don't go to a shop boring cylinders with a hand drill. They have no idea what they are doing. If anyone can't find a good shop PM me I'll size your cylinder properly for $50, which includes return shipping.