401963
L plate rider.
Posts: 26
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Post by 401963 on Sept 3, 2019 22:49:29 GMT 1
Evening everyone , been reading the forum for quite a while now an decsided to join , I to have a TWO/ STROKE addiction Its good to talk and then hopefully i can get help , Seems some of you have got i worse than me , Now hear is the issue Yamaha 350lc 4lo fitted with standard power valve motor + loom , original ypvs ran fine since relocating into 4lo it seems to have picked up a misfire , when starting up choke out rus with out issue , choke in go`s down on left hand cylinder : swopped carb 31k units ultrasonic cleaned + brass balls out no change , swopped coil same , changed reed blocks + reeds , new plugs correct gaps , checked timming , same ,,,,,,,,,,,,,,argh , tonight did compression test left cylinder 35 right hand cylinder 40 ? , trying to find out what standard compression is for standard 350lc ypvs 1ua ? , sorry for going on but the more information an hopefully someone may know the answer ....................... many thanks . paul
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Post by dusty350 on Sept 4, 2019 7:27:44 GMT 1
Hi Welcome to the forum Compression figures seem very low. You are looking for well above 100psi - 115 to 120 I believe, on a healthy engine that's been warmed up. Seems odd that it was fine until you swapped the engine into the 4l0. What is the history on the Pv engine ie, when was it last rebuilt, parts used etc. Could be fuelling as you say it runs fine on choke but not off it. Also check your earth points on the frame - that's something that would have changed during the conversion. What wiring loom did you use ? Dusty
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401963
L plate rider.
Posts: 26
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Post by 401963 on Sept 4, 2019 19:13:13 GMT 1
Thanks for the welcome Dusty , I have read alot of your posts with intrest an attention to detail with your builds ( fantastic ) . The bike is running a standard f2 1ua the only thing not conected is the rev counter (electric) as running 4lo clocks the wires have been taped off an tucked into clock housing , i will run the bike up to temp an retest compression again , also double check earths , also the bike was used about 2 years ago an rode ok thats whats so strange ............... thanks for the advice ...........paul
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Post by oldbritguy on Sept 4, 2019 22:41:18 GMT 1
Looking forward to your findings as quite intrigued.
Oh! and well done for finally joining the forum and a warm welcome
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Post by stusco on Sept 4, 2019 22:48:06 GMT 1
Is it my imagination or is your font getting smaller ,think about us old guys and our poor eye sight
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Post by dusty350 on Sept 5, 2019 6:30:09 GMT 1
I wonder if the piston rings are gummed up from sitting ? As you say, a top end refresh may be needed. And if you ever have the cases apart, you can retro fit a mechanical speedo drive which would enable you to run the Lc tacho via a cable. Good luck Dusty
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Post by midlifecrisisrd on Sept 5, 2019 8:37:28 GMT 1
I wonder if the piston rings are gummed up from sitting ? As you say, a top end refresh may be needed. And if you ever have the cases apart, you can retro fit a mechanical speedo drive which would enable you to run the Lc tacho via a cable. Good luck Dusty You may be right on the money there Dusty Had a bike years at a that had been lying and ran like crap I'd strip it, checked everything and put it back together. It would run fine for 30 seconds then lose power. Turned out to be the rings gummed up and sticking as soon as some heat went in. If the RH ain't gummed at 95psi it's rebored time I'm afraid Steve
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401963
L plate rider.
Posts: 26
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Post by 401963 on Sept 5, 2019 22:55:09 GMT 1
Evening lads , Stusco / Oldbritguy / midlifecrisisrd / Dusty ,,,,,,,,,,,,,,,,,, You guys sort of nailed it , removed head after tea , left hand side pitted ( oh 5hit ) removed barrel ( ok ) , then looked at the piston OH BUGGER , looks like lower piston ring did not like the crinkley ring underneath , 1 third of ring missing . the top ring complete but as broken ring exited upwards squeezed past and pinched top ring in the slot , That would explain flames and sparks out the left hand pipe , So yeah piston rings sort of stuck rebore time ,,,,,,,,,,,, Question when i get 2 x pistons + rebore do i fit the crinkley ring under the bottom ring again or can i leave them out ? , once again thanks for your input great help . many thanks paul
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Post by dusty350 on Sept 6, 2019 7:35:43 GMT 1
There has been a recent thread on the expander ring. Lots leave it out with no issues. I never fit them, although all the recent Mitaka sets I have bought don't have them included anyway. Just be absolutely sure none of the broken bits ended down in the crank area Dusty
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401963
L plate rider.
Posts: 26
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Post by 401963 on Sept 8, 2019 22:26:00 GMT 1
Thanks for the info Dusty , Not being nosey but where do you get your makita piston sets from ( internet or local source ) , I notice on alot of your threads you seem to use companys in and around Reading , I am not to far away as down in newbury ,,,,,,,,,,,,,,,,,,,,Many thanks paul
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Post by dusty350 on Sept 9, 2019 7:47:05 GMT 1
Hi Paul, I use PJME in Wolverhampton (Wednesfield), for my rebores and crank rebuilds. They have done tons for me over the years. Be aware there are Jap made Mitakas, and Taiwanese Mitakas available from various sources. Make sure you get the Jap made ones. Pjme only do the Jap ones. The only firm I've used near Reading is R.D Cox in Whitley Wood for vapour blasting. I used to live in Early 22 years ago so they were local for me then. Think there is another member on here from Newbury, but cant remember who it is Dusty
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