top end rebuild questions

[ukweasel]

so my blaster had low compression and i suspected it was time for new top end. i tore it down today and my suspicions were confirmed. i took the cylinder and piston to the local shop and they recommended 1mm size up on the piston, which is a 67 mm (66 being factory). when i put this thing back together will i need to rejet? the bike is bone stock and im not looking to spend money on aftermarket parts to make this thing run right again. can someone please advise?

also, the tors has been disconnected, and i suspect the oil pump does not work right and plan on blocking it off and premixing. rather than buy a block off kit, would it be ok to cram a nail and seal the oil line to the carburetor off? what do i need to put back in place of the oil pump? and does the sensor in the oil reservoir need attention while im at it?

also, what is the proper ratio for gas/oil with this set up, and is it ok to run quicksilver 2cycle outboard oil, or is there a particular oil i need to grab that will do best? thanks in advance for any advice.

[ukweasel]

can someone just comment on the need for a rejet after going to that bore size? i found most of the other info on another forum's website.

[allsmilez620]

no you dont have to re-jet only if you have a filter an air box mod

[ukweasel]

finally got it all put back together, runs great, but definitely needs a rejet. the only way i can get it to run without coughing and backfiring is to turn the air screw all the way in. im guessing i need to go up on the pilot and probably go up 2 on the main, and maybe a needle clip position? does anyone concur or have any input?

[fearlessfred]

u are on the right track when u switched to pre mix u leaned it out what elevation are u at

[ukweasel]

705 feet roughly. i live in northern alabama. just a recap, the blaster was completely stock (to my knowledge) and i just put a 67mm piston in it and removed the oil injection. thanks for the reply

[fearlessfred]

yea u are close to sea level i would proceed as u planned the airbox lid being off and running premix instead of the oil injection would both lean it out

[ukweasel]

when i put it back together it kept revving reall high for no reason, guessing cuz it was so lean (checked for leaks around carb boot and there were none). but i turned it off and it started dieseling and got stuck at wot for like a minute and a half while i was running frantically looking for a plug wrench. had it not caught me off gaurd so bad i prolly would've had the common sense to put it in gear and dump the clutch, but it was in my shop so it didn't occur to me at the time. prior to it doing this i had let it idle while i lightly feathered the throttle for about 20 minutes or so and then let it completely cool. i didnt start it again until the next day is when i took it out and it did fine minus the apparent need for a rejet. the bike doesn't smoke anymore than i would expect it to really so no obvious signs of cranks seal damage, and the motor pulled pretty strong, it did give me a scare when the spark plug wiggle loose and killed the compression though but put it back in and did fine. if the wot situation was going to do serious damage would it be obvious by now or have i created a ticking time bomb?

[ukweasel]

ok so i went over today to crank the thing up and give it a gentle ride, smoked like a fog machine. im guessing definitely crank seal needs to be replaced. do i need to do both sides or only the clutch side? is there anything else i need to be concerned about possibly damaging? crank bearings or rod bearings? what are symptoms and does it make any strange noises? i did a compression check and im at 120 psi after everything. any help would be appreciated.

[ukweasel]

just in case anyone encounters the same issues i did...i replaced both crank seals. the one on the clutch side is an absolute pita to get out so if you read "oh its easy" dont count on it lol. mecahnical/technical ability is easy, but it takes some serious force and i had to use a good steel hook to pull it out.

now that everything is all back together, it runs fine, but i cannot get it to idle unless a turn the air screw all the way in. even then, the tors idle screw has no effect so i guess i will continue to monkey with it