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Post by bobbygt on Jul 13, 2020 19:14:32 GMT 1
Hello all new to the forum at present having spent most of my time with british bikes bsa triumph and the like now fancy getting into jap 2 strokes so having a go at restoring a 4l0 350 lc having problems with crankshaft s have numerous cranks with spun magneto side bearings all ? on shaft not cases ,got impatient with my progress and ordered a new taiwan crank with jap bearings and con rods from a well known and respected engineer first crank that came i thought was bad 3 thou run out at mag side and 5 tho at primary side contacted the engineer add asked to return item and was assured it would be sorted they sent another crank spins lovely but run out is still 5 thou at primary ant 2.5 thou at mag, am i expecting to much of these units my background is marine engineering where these tolerances would be rejected please advise will my lc run ok with 5 thou run out on the primary drive gear and will my flywheel run fine with 2.5 thou run out thank you in advance for any input
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Post by dusty350 on Jul 13, 2020 19:38:09 GMT 1
Hi Welcome to the forum I think the manual states 2.5thou run out is acceptable. I had my 400e crank rebuilt by Paul at PJME in Wolverhampton back in March, and he has seen as much as 12 thou on some cranks. He aims to rebuild a crank with zero run out. I did a thread on it here; rdlccrazy.proboards.com/thread/50276/crank-rebuildMight be of interest to you. Enjoy the forum Dusty
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Post by Tobyjugs on Jul 13, 2020 19:58:02 GMT 1
Hi welcome to the forum. Can you explain how you are measuring the crank shaft deflections?
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Post by bobbygt on Jul 13, 2020 21:27:57 GMT 1
Hi welcome to the forum. Can you explain how you are measuring the crank shaft deflections? Thanks i use a dial gauge with crank bolted in cases fixed to engineers table magnetic base for gauge
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Post by Tobyjugs on Jul 13, 2020 23:32:29 GMT 1
Your method sounds the most logical but i have measured cranks made by myself (tiny bit wonky and quite good) and cranks from the professionals which have all been in tolerance on rollers and between centres. When you put them in engine cases and torque the cases up they sometimes deform and you will get those out of tolerance deflections. I would not fix the engine to a table this could also have an effect on your measurements. I bolt a small strip of steel to the engine and fix the magnet to the steel strip a bit like below. In the past i have adjusted them with a large copper hammer until the deflections were tolerable. If you do adjust the crank yourself the primary drive side is important as this side will have an effect on your primary gearwheel tolerances.
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Post by bare on Jul 14, 2020 3:36:37 GMT 1
This is for an LC /4l0 then?? IMO yer Hooped then as it's Unlikely to source a factory fresh 4l0 Crank. Alternate is a Genuine Yamaha Banshee crank. Yess.. it can be fitted into 4l0 cases. Either it drops right in (dependant on the mfg Date on the 4l0 cases) Or (in worst case scenario) you pay a shop to fly cut the cases to accept the slightly wider crank assly. Easy and reasonably inexpensive. NOT cheap for the Genuine article Crank though ..but the 'Clones' are by and large Junk.. Despite fanboy claims and alleged Pedigree. Simply a Bad Buy... Avoid ! Try one and learn this Firsthand :-) Genuine Yama cranks tolerate ~ 3 rebuild pressings before the interference fits become sketchy. Clones typically cannot tolerate even One re pressing. Some fail /twist within a few hours run time.. even the 'welded' ones.. Geeez ! Chinese are infamous for Cheating on Hardening specs.. along with all other 'specs' G luck.
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