Jump to content
Sign in to follow this  

Top end rebuild

Recommended Posts

Hi guys, i ordered a 54mill Wiseco piston and rings for my cr125 the other day and when i got it there was nothing stating what the ring gap needs to be. I pushed the ring in the bore and there is no gap at all so does anyone know what the gap needs to be?

Thanks.

Share this post


Link to post
Share on other sites

wiseco says multiply your bore size in inches by .004.

i dont know anything about 125's, is that 54mm exactly or 54.xx mm? according to wiseco youd need 0.008" of ring gap.

i can tell you though that for my cr250, according to wiseco id need 0.010" of ring gap but the brand new ring started at 0.013". either my bore is worn out, or the 0.004" per inch of bore spec isnt quite right.

Share this post


Link to post
Share on other sites

theres not a exact amount of end gap but rather a window of acceptable range. for instance if you read the owners manual regarding oem rings, they can have a gap any where between .016-.022 with a max limit of .026, (cr250). if your gap was any where between .016-.026 your good. on wiseco rings that ive bought, theres always some instructions inside the package. if theyre missing just call their tech support. may need even more gap with modified engines. it wouldnt be uncommon for a set of wiseco rings to be tight and need alittle grinding to open up the gap. the instructions clearly tell you that.

Share this post


Link to post
Share on other sites

Thanks guys, yeah the piece of paper was missing. And mynewcr250 its exactly 54mm

Share this post


Link to post
Share on other sites
theres not a exact amount of end gap but rather a window of acceptable range. for instance if you read the owners manual regarding oem rings, they can have a gap any where between .016-.022 with a max limit of .026, (cr250). if your gap was any where between .016-.026 your good. on wiseco rings that ive bought, theres always some instructions inside the package. if theyre missing just call their tech support. may need even more gap with modified engines. it wouldnt be uncommon for a set of wiseco rings to be tight and need alittle grinding to open up the gap. the instructions clearly tell you that.

This. .016-.022. File your ring down to meet that spec. I go by the honda specs.

Share this post


Link to post
Share on other sites
Thanks guys, yeah the piece of paper was missing. And mynewcr250 its exactly 54mm

ok, so yea that would put you at 0.0085" according to wiseco.

if you go by honda specs, you are gonna go much bigger, but honda uses a cast piston while the wiseco is forged. id assume wiseco knows exactly how much more/less a forged piston will expand and gives you a ring end gap spec that is known to work for their pistons.

if you call wiseco they will tell you 0.004" per inch of bore. thats what the missing paper you didnt receive says. id be more apt to use wiseco ring spec for wiseco pistons, although id still go for something like 0.010" to 0.012. that first spec just seems awful tight to me but i dont have experience building performance engines, id just be a little on the cautious side. even so, the paper thats missing will say something along the lines of "generally" this ring gap works for most applications. i guess it wouldnt hurt and see if they ask for any specific gap setting your application.

Share this post


Link to post
Share on other sites

I think i will go for 0.009" so its just a bit more then Wiseco says. I will let you all know how it goes.

Cheers.

Share this post


Link to post
Share on other sites

I put it together with 0.009" ring gap and it ran perfectly, just finished breaking it in and hope to take it for a ride this weekend.

Thanks for all your help guys.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×