Rebuilding this winter- REBUILDING NOW-RING GAP QUESTION

NightBiker07 · Post by **NightBiker07** » September 21st, 2009, 3:11 pm

Rebuilding the 250 this winter. dont know the history of the thing, and want to make sure its in top shape for next year.

could be me, but it seems like there is a slight knock at low RPM. ive heard motors make this noise a LOT louder in the past and have held together perfectly fine, but like i said, i dont know its history. its definitely not piston slap because it isnt high pitched like piston slap, and it doesnt get louder as the bike rev's up, you cant even hear it in the slightest when your out romping on it. only at an idle and lugging it in the woods. it is more noticeable when its cold too.

The bike runs great, if the consensus is that the motor is gonna be a bit noisy, ill just take the top end apart and look at the piston and check the play in the bearings. If the piston looks good and bearings arent sloppy, ill probably run it another season. The motor has awesome compression and runs great and was supposedly rebuilt in the top end when i bought it.

so, i would assume that by the time i buy a rod kit and pay a shop to assemble the crank, i could just buy a new crank assembly.

Should i go with a Hotrods crank assembly? they are all over Ebay BNIB for around 180-220 BIN. or are there better options for the $?

obviously, it will also get new bottom end bearings/seals, and a new piston/ring combo.

If the bore isnt messed up, i can just get a new STD (or whatever bore it is on) size piston, have the rings ground for proper end gap, and assemble it with a light hone, correct?

thestuz · Post by **thestuz** » September 22nd, 2009, 3:18 am

ive heard oem conrods are the go. when i rebuilt my motor the oem conrod was so good i didnt even bother replacing it. and if i were you id just rebore.

thestuz · Post by **thestuz** » September 22nd, 2009, 3:20 am

ive heard oem conrods are the go. when i rebuilt my motor the oem conrod was so good i didnt even bother replacing it. and if i were you id just rebore if its steel bore.

NightBiker07 · Post by **NightBiker07** » September 27th, 2009, 8:06 am

well, rebuilding sooner than expected. motor lost compression while i was flogging it out on a track, unfortunately, i made a 4 hour trip to go riding when it fried :/

im tearing it apart now to see what happened. it didnt sieze tho

caseyracing222 · Post by **caseyracing222** » September 27th, 2009, 9:43 am

that knock you are hearing is probably the lower main bearing to the connecting rod, the bearing cage probably shattered. That happened to my yz and shortly after it lost all compression. since you have a newer bike I would just buy a complete new rod assembly, it will only be about 20 dollars more. I think the hotrods crank is good and its easy on the wallet, oem cranks arent cheap. good luck with your build

NightBiker07 · Post by **NightBiker07** » September 27th, 2009, 3:02 pm

caseyracing222 wrote:that knock you are hearing is probably the lower main bearing to the connecting rod, the bearing cage probably shattered. That happened to my yz and shortly after it lost all compression. since you have a newer bike I would just buy a complete new rod assembly, it will only be about 20 dollars more. I think the hotrods crank is good and its easy on the wallet, oem cranks arent cheap. good luck with your build

yep, after disassembly, the lower rod bearing is shot. crank bearings feel tight as can be though.

the bore is nearly perfect, except for one groove where something happened to the piston, so it needs bored.

caseyracing222 · Post by **caseyracing222** » September 27th, 2009, 4:28 pm

even if your bearings feel fine now you should replace them, peices from the rod bearing are probably stuck in the case bearings, also the score in the piston is probably from pieces of the rod bearing squeezing up the cylinder. I have pics of my bike if you want to compare.

NightBiker07 · Post by **NightBiker07** » September 27th, 2009, 4:33 pm

Hmm. many piston choices. Wiseco, Pro-X, OEM......which one should i go with?

EDIT- ordered the first oversize Wiseco, with a cometic gasket kit.

gonna order the crank tomorrow after i stop by the bank.

Wiseco crank assembly, with bottom end bearings/seals, AND bottom end gasket kit, 189.99 shipped. unless wiseco cranks are junk?

caseyracing222 · Post by **caseyracing222** » September 27th, 2009, 6:43 pm

wiseco piston was a good choice, as far as the crank? I've never heard of a wiseco crank for a dirtbike until now

NightBiker07 · Post by **NightBiker07** » September 27th, 2009, 6:50 pm

caseyracing222 wrote:wiseco piston was a good choice, as far as the crank? I've never heard of a wiseco crank for a dirtbike until now

yeah, they are all over the Bay. same with their bearings/seals. i would imagine they are a quality part, never heard bad things about wiseco.

what about Namura? they are substantially cheaper, and i cant find any actual user stories on the net, good or bad. anyone gave them a shot?

seanmx57 · Post by **seanmx57** » September 28th, 2009, 5:26 pm

for what U R going to get into that rebuild you would be well on your way with a 500.

Thinking your going to learn to utilize the power of a 250 is optimistic. 500's are easier to ride cause the don't require as much skill.

100hp honda · Post by **100hp honda** » September 28th, 2009, 5:29 pm

seanmx57 wrote:for what U R going to get into that rebuild you would be well on your way with a 500.

Thinking your going to learn to utilize the power of a 250 is optimistic. 500's are easier to ride cause the don't require as much skill.

someone already suggested that. says hes skeeered of the 500. so we are helping him rebuild the 250

NightBiker07 · Post by **NightBiker07** » September 28th, 2009, 7:14 pm

seanmx57 wrote:for what U R going to get into that rebuild you would be well on your way with a 500.

Thinking your going to learn to utilize the power of a 250 is optimistic. 500's are easier to ride cause the don't require as much skill.

I wouldnt really say its optimistic. a 125 already doesnt have enough OOMPH. i dont have a problem keeping the motor in the powerband most of the time, but rather how much throttle i am using into a berm lol. im getting there, problem is i only ride the damn bike once every 2 weeks or so. if i could get on it twice a week, i'd be a lot better off.

100hp honda wrote:
seanmx57 wrote:for what U R going to get into that rebuild you would be well on your way with a 500.

Thinking your going to learn to utilize the power of a 250 is optimistic. 500's are easier to ride cause the don't require as much skill.
someone already suggested that. says hes skeeered of the 500. so we are helping him rebuild the 250

exactly

im not so much scared of it, it would actually come in handy for some hillclimbing and trailriding, but for MX it would be extremely under utilized.

seanmx57 · Post by **seanmx57** » September 29th, 2009, 6:31 pm

I feel handy capped with out the 500 doin MX now. My motor is on the bench again, building a new chassis so I'm stuck on the 250. Seems like I'm riding a 125 again.

500's are easily detuned with a simple rear sprocket change or richen it up so you got black spooge all over everything. I could barely ride the 500 stock doin MX at first, I had to liven up the motor considerably, but I was used to a Pro Circuit built 250 2 stroke that hit hard and hauled butt.

Ride a gear high and the 500 is pretty mellow, definately easier than a 250 to handle a gear high. But downshift and pay your health insurance. In the right gear set up right it will piss off everyone that U get near until U get tired.

Junk that 250 motor on ebay

NightBiker07 · Post by **NightBiker07** » October 2nd, 2009, 12:31 pm

Im impressed. the Wiseco kit i bought for 200 bones came with a crank, main bearings, and all the gaskets AND bottom end sealsm for even the sprocket shaft, shifter, and kicker. im impressed, and it all came in a WISECO box. ill post pics of it later

hoofarted · Post by **hoofarted** » October 2nd, 2009, 1:03 pm

lemme know how she runs...my 01 250 motor is all original still!

seanmx57 · Post by **seanmx57** » October 2nd, 2009, 4:43 pm

NightBiker07 wrote:Im impressed. the Wiseco kit i bought for 200 bones came with a crank, main bearings, and all the gaskets AND bottom end sealsm for even the sprocket shaft, shifter, and kicker. im impressed, and it all came in a WISECO box. ill post pics of it later

Was that $200 retail?

NightBiker07 · Post by **NightBiker07** » October 2nd, 2009, 9:06 pm

seanmx57 wrote:
NightBiker07 wrote:Im impressed. the Wiseco kit i bought for 200 bones came with a crank, main bearings, and all the gaskets AND bottom end sealsm for even the sprocket shaft, shifter, and kicker. im impressed, and it all came in a WISECO box. ill post pics of it later
Was that $200 retail?

technically, it was a little over 200, i think like 207. but no, it wasnt retail. fleabay.

Heres the kit, followed by the carnage. the main box it all came in has Wiseco plastered all over it, and the gasket kit is a Wiseco kit too.

The piston looks a million times worse than the bore. the inside of the crankcase has a few chew marks. whatever came loose bounced around a bit, but i never found the loose item.....

CR500R7 · Post by **CR500R7** » October 3rd, 2009, 3:37 am

The bottom 4 photos are they spy photos from brit's garage?

NightBiker07 · Post by **NightBiker07** » October 3rd, 2009, 11:20 am

CR500R7 wrote:The bottom 4 photos are they spy photos from brit's garage?

lol, its the garage i have at my apartment. still working on getting a good workbench and some other things to make it a decent work area

NightBiker07 · Post by **NightBiker07** » October 5th, 2009, 6:00 pm

shipped the cylinder to millennium, along with the Wiseco pro-lite. should be back in a week and a half

NightBiker07 · Post by **NightBiker07** » October 15th, 2009, 10:04 pm

Got my cyl. back, millennium did a awesome job!

now, for a question.

going by wiseco's doo dicker, you should multiply the bore by .004 for the top ring, and the bore by .005 for the bottom ring to come up with the end gaps.
bore is 2.6126

going by this, i get .010 (ten thou) for the top ring end gap, and .013 for the bottom ring end gap.

does this sound correct, or am i missing something entirely? i'd hate to size the motor from improper ring gap.

thestuz · Post by **thestuz** » October 15th, 2009, 11:48 pm

noy too sure man. it usually has the exact ring end gaps on the box. not sure about the multiplication bit. sounds like a question for alisobob. i thought your bore would be width. say 91mm x .004(imp/or metric)

CR500R7 · Post by **CR500R7** » October 15th, 2009, 11:53 pm

No man, he is rebuilding his CR250 engine, so it is only about 66mm or what he had in "s.

thestuz · Post by **thestuz** » October 16th, 2009, 2:40 am

thanks cr7, i was just using that as an example

BannedCR500Riders.com

Rebuilding this winter- REBUILDING NOW-RING GAP QUESTION

Rebuilding this winter- REBUILDING NOW-RING GAP QUESTION