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stock bore size is 66.4mm or 2.614 inches. when checking the bore with a good set of calipers, it comes out to be about 2.612 inches. i'd get a better reading with a mic, but i dont have one.

going by that measurement, its on its first bore, i mean, a 2 thousandths difference between my measurement and std. bore can be attributed to the caliper not being perfectly square in the bore.

are oversizes going by .5mm or 1mm?

89mm is standard bore for the 500, oversizes go 89.25-89.5+up to 91mm from wiseco,prox+vertex

.25mm is .0010"

Roostius_Maximus wrote:89mm is standard bore for the 500, oversizes go 89.25-89.5+up to 91mm from wiseco,prox+vertex

.25mm is .0010"

Thanks. i just ordered the next size up Wiseco for my bike, a 67mm.

Thanks!

NightBiker07 wrote:

Roostius_Maximus wrote:89mm is standard bore for the 500, oversizes go 89.25-89.5+up to 91mm from wiseco,prox+vertex

.25mm is .0010"

Thanks. i just ordered the next size up Wiseco for my bike, a 67mm.

Thanks!

i have a few questions. ( i believe your cylinder is nikisil) what went wrong that the bore is no good ? since you went with a larger piston, now you have to bore it and re nikisil, the bore process will add extra expense and you really dont need. IF there is something wrong with the bore, you would been better off just buying standard piston and replating back to standard (eliminating the boring charge). im wondering how much damage you actually have. my 440 is 15yers old, still original nikisil/piston/seals/bearings........believe it or not thats 100% true story. nikisil lasts forever man, i would double check you actually need all that work before forking out the cash.

100hp honda wrote:

NightBiker07 wrote:

Roostius_Maximus wrote:89mm is standard bore for the 500, oversizes go 89.25-89.5+up to 91mm from wiseco,prox+vertex

.25mm is .0010"

Thanks. i just ordered the next size up Wiseco for my bike, a 67mm.

Thanks!

i have a few questions. ( i believe your cylinder is nikisil) what went wrong that the bore is no good ? since you went with a larger piston, now you have to bore it and re nikisil, the bore process will add extra expense and you really dont need. IF there is something wrong with the bore, you would been better off just buying standard piston and replating back to standard (eliminating the boring charge). im wondering how much damage you actually have. my 440 is 15yers old, still original nikisil/piston/seals/bearings........believe it or not thats 100% true story. nikisil lasts forever man, i would double check you actually need all that work before forking out the cash.

the bore has a decent groove in it. one overbore will surely take the groove out, so its not a gouge or anything. looks like a piece of the rod bearing got wedged in between the piston and the cylinder. other than the one line of damage going down the side of it, the rest is fine. even if it is nickel plated, does it really matter? i mean, plenty of other motors arent nickel plated.

i just contacted the seller, told him to wait on sending my piston, cause he can send a STD. bore piston if needed.


if re-nickeling is the most adviseable route, where should i take it? im sure the local racing shop can have it sent out, but is there any price baseline i should expect, or any companies i can ship to have it done for a fair price?

NightBiker07 wrote:

100hp honda wrote:

NightBiker07 wrote: Thanks. i just ordered the next size up Wiseco for my bike, a 67mm.

Thanks!

i have a few questions. ( i believe your cylinder is nikisil) what went wrong that the bore is no good ? since you went with a larger piston, now you have to bore it and re nikisil, the bore process will add extra expense and you really dont need. IF there is something wrong with the bore, you would been better off just buying standard piston and replating back to standard (eliminating the boring charge). im wondering how much damage you actually have. my 440 is 15yers old, still original nikisil/piston/seals/bearings........believe it or not thats 100% true story. nikisil lasts forever man, i would double check you actually need all that work before forking out the cash.

the bore has a substantial groove in it. looks like a piece of the rod bearing got wedged in between the piston and the cylinder. other than the one line of damage going down the side of it, the rest is fine. even if it is nickel plated, does it really matter? i mean, plenty of other motors arent nickel plated.

the difference in boring a nikasil cylinder and a steel bore is the nikasil cylinder has an aluminum bore so the rings wont seal. I would suggest re sleeving your cylinder to a steel bore or re nikasiling if you dont mind waiting 8 weeks for it to get done, or you can spend about 50 to 75 more dollars and get a brand new cylinder from honda.

100hp the previous owner of your 440 must have not of ridden it much or not very hard, my 98 250 has been through two nikasil platings, I wore through one and chipped and cracked the other.

depends how deep the scratch is. the scratch can be .007 deep before needing welded or bored. i was thinking financially how you would come out better off. you already bought the piston, so your kind of stuck with it now. good luck man

caseyracing222 wrote:100hp the previous owner of your 440 must have not of ridden it much or not very hard, my 98 250 has been through two nikasil platings, I wore through one and chipped and cracked the other.

my 440 motor is 50 times stronger in EVERY aspect than a 250. beleive me it was rode and rode plenty, but not abused like 99% of the bikes out there. my bikes get rode the same as everyone elses, aint been no seizures or crank bearing failures at my house . its all in what ya know

millenium does a fine job. costs $210, that included round trip shipping plus new plating. if your scratch is under .007, you wont have any addition costs, if its deeper your either have to bore or have it welded.

well, like i said, i contacted the seller and told him to wait on shipping me the piston. it helps that i didnt pay for it yet, so nothing is going to be shipped anyways. the auction was set up so i had to mention in the details that i needed an overbore, and to request total. so, i hadnt paid for it yet.

no big deal

Have you thought about just doing your 250 to 5 hundy conversion a little earlier and save the money from the 250 rebuild, just a thought.

CR500R7 wrote:Have you thought about just doing your 250 to 5 hundy conversion a little earlier and save the money from the 250 rebuild, just a thought.

yes, i have. problem is, no local cr500's around here for anything close to reasonable. i still havent harnessed the 250's power yet either, im afraid of it lol. but i can fully utilize a 125, so im getting there. mind you, ive only been on a fast bike for about a year. after i utilize the power of the 250 a little better, i will start pounding the ground for a 500.

the head has a fair amount of detonation pitting/marks, and am wondering if this means i need to get a different head or what. i dont see how it would adversely affect the motor, other than a lower compression?

NightBiker07 wrote:the head has a fair amount of detonation pitting/marks, and am wondering if this means i need to get a different head or what. i dont see how it would adversely affect the motor, other than a lower compression?

I assume your head looks like this



you dont need a new head, get some emry cloth in 180, 240, and 400 grit. Before sanding the head alot of your "detenation" marks are pieces of bearing from your rod so pull them out with some needle nose plyers, then start off evenly sanding the burs on your head with 180 and progressivley work your way up to 400 grit. This prossess takes about a 1/2 hour, you wont loose any compression.

yep. thats exactly what the head looks like. so, im just looking to take out any loose particles and deburr the thing, correct?

yep!

why do you figure the bearing went out ? lets get bob to chime in . i know it goes against everyones rational thinking but i been religiously putting 26:1 beenoil in my 500 since about last november, the 250 i put R50 so the powervalve doesnt gum, the ktm's are running 26:1 beenoil also. the more oil you can pump through the better off you are, gordon jennings proved it in his book.

100hp honda wrote:why do you figure the bearing went out ? lets get bob to chime in . i know it goes against everyones rational thinking but i been religiously putting 26:1 beenoil in my 500 since about last november, the 250 i put R50 so the powervalve doesnt gum, the ktm's are running 26:1 beenoil also. the more oil you can pump through the better off you are, gordon jennings proved it in his book.

ive run 32:1 or richer using Super Techniplate. ever since i got the bike, its has a very slight knock. when i took it apart, the lower rod bearing has sloppy side to side play and a touch of up-down play. and since looking at the size of the groove in the cylinder, it is about the width of a piece of one of the needle bearings. thats the only thing i can figure happened to the otherwise perfect cylinder walls.

NightBiker07 wrote:

100hp honda wrote:why do you figure the bearing went out ? lets get bob to chime in . i know it goes against everyones rational thinking but i been religiously putting 26:1 beenoil in my 500 since about last november, the 250 i put R50 so the powervalve doesnt gum, the ktm's are running 26:1 beenoil also. the more oil you can pump through the better off you are, gordon jennings proved it in his book.

ive run 32:1 or richer using Super Techniplate. ever since i got the bike, its has a very slight knock. when i took it apart, the lower rod bearing has sloppy side to side play and a touch of up-down play. and since looking at the size of the groove in the cylinder, it is about the width of a piece of one of the needle bearings. thats the only thing i can figure happened to the otherwise perfect cylinder walls.

Night biker has all the symptoms of a lower rod bearing failure

sounds like the previous owner had alot to do with it. maybe some sand went through.

caseyracing222 wrote:

NightBiker07 wrote:

100hp honda wrote:why do you figure the bearing went out ? lets get bob to chime in . i know it goes against everyones rational thinking but i been religiously putting 26:1 beenoil in my 500 since about last november, the 250 i put R50 so the powervalve doesnt gum, the ktm's are running 26:1 beenoil also. the more oil you can pump through the better off you are, gordon jennings proved it in his book.

ive run 32:1 or richer using Super Techniplate. ever since i got the bike, its has a very slight knock. when i took it apart, the lower rod bearing has sloppy side to side play and a touch of up-down play. and since looking at the size of the groove in the cylinder, it is about the width of a piece of one of the needle bearings. thats the only thing i can figure happened to the otherwise perfect cylinder walls.

Night biker has all the symptoms of a lower rod bearing failure

uh ya we already know that . question is why. replacing rod bearings every couple years isnt normal. sounds like it was trashed from the previous owner.

Like you said 100hp the previous owner probably neglected it and ran recycled chainsaw oil

back in the day i think they used motor oil. or maybe that was MFDB that used motor oil on his air filter. hell i cant remember

previous owner raced. bike had a new top end on it when i bought it, must have neglected the lower end. probably running the same crank from the factory. not too big of a deal, ive got 800 into the bike when i bought it, plus fork seals/bushings. no other parts have been added, and the tranny is tight. so i am still money ahead on the whole deal.