OzVMX Forum
Clubroom => Tech Talk => Topic started by: YZ250H on April 03, 2011, 12:48:51 pm
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Hi Fellas,
A little help if I may. Bought this bike a few months ago. Ad said it "runs well". Bullshit.
When I got it home it had no spark. >:( So after replacing the coil and sorting out the incorrect wiring (wire earthed that should have gone to normally open kill switch) I thought I should be in the clear. Bullshit.
Discovered a crack in the inlet manifold from the carby. Put a new one on and replaced the airfilter with a (sexy) GMC box and YZ85 filter. Replaced Airbox boot (someone had put a CV joint boot on there :o :o )
So I should be good to go - right..... Bullshit.
Checked timing, float level, cleaned carb....... Still no go despite two of us taking turns at pushing it up and down the road.
I thought I had covered off everything - the only other thing I can think of is crank seals. One of these has to be replaced from the inside, so looks like I'm splitting the cases - not a big deal, put a pain in the bum. :'( :'( :'(.
The ad did also say that it had been sitting in the shed for years :-\
Am I missing something ???. Should the damn thing at least start even if the crank seals are shot ?? :-\
Help please
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Should start even with a leaky seal. I saw a bike start and run with a seal not even installed on the stator side! It was running a little lean though :D
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Does it fire at all? Any sign of ignition happening when being pushed? Consider checking the timing with a stobe light to double check its in the ballpark. I had a bike that had spark and fuel but wouldnt start - turned out timing was 90 degrees out ::) ::)! Keep persevering you'll get the sucker running ;D ;D
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how shiny is the pipe? maybe it needs polishing?
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Does it fire at all? Any sign of ignition happening when being pushed? Consider checking the timing with a stobe light to double check its in the ballpark. I had a bike that had spark and fuel but wouldnt start - turned out timing was 90 degrees out ::) ::)! Keep persevering you'll get the sucker running ;D ;D
The best I can get is a backfire when I give it a gob full of "start ya barstard". Thinking of getting a can of "Oh come on". If that doesn't work a can of "Pleeease". ;D ;D ;D ;D
Good strong spark. Maybe it is out as you say. If the CR has a woodruff key like the yammies how can it be out so far ?
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if a backfire is as good as it gets i'd bet money on the timing being out.
so the million dollar question Tony,
whats the timing currently set too BTDC?
and never put too much faith in those woodruff keys, i've sheared a few of them and my 125 doesn't even have one fitted.
timing dude.
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I bet the stator is 180 deg out or is firing ATDC which backfiring is a sign of. No more cans and out with the dail gauge and holder.
Technicaly the bike does run, if your pushing it ;D
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I'm on it ;) I'll pull the flywheel off and see if anything dodgy is going on ;)
Of course I don't have a puller that fits... bloody Hondas ;D ;D
I'm just off to Ebay now ::) ;D ;D
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Done - just have to wait 10 days for Ebay Santa to arrive ;D ;D ;D ;D
I love Ebay Santa
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Try with the pipe taken off.
Sometimes small animals will make a home in the pipe and stop it from running.
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Use a strobe and you dont need to wait for the puller - I find el cheapo from SCA does the trick if you can do it in dim lighting.
Remember you cant tell when it fires mechanically - all you can do is set it up so stator and flywheel are correctly aligned at the specified mm BTDC. Only a strobe light can tell you for sure if thats when it actually fires ....everything else is based on the assumption that the stator and flywheel are triggering the spark when they are correctly aligned. If you have had the stator repaired or rewound this can be stuffed up during the repair! If it is unmolested then chances are it still works as per factory setting.
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I've got 10 days to wait, so what have I got to lose. I'll send the Missus off to Supercheap :D
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Try with the pipe taken off.
Sometimes small animals will make a home in the pipe and stop it from running.
Yeah, mainly those "common greasy chamber rats" their prolific up on the tablelands -little bastards !!! :D :D :D ;D
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Try with the pipe taken off.
Sometimes small animals will make a home in the pipe and stop it from running.
jeez Tony, have you checked your Gerbil pen to see if any are missing?
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There is one missing - the one I lent you :o :o :o
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whats the compression like.must be over 100psi to get it to run.my yz125x would backfire and run as long as you pushed it as soon as you stop pushing it stopped.
checked psi it was 55.
getting bored as we speak pick the barrell up on friday.the motor now will be new top and bottom
jim
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I'm told it is new top end Jim. Compression feels Ok on the kicker :-\
This thing won't even fire despite being pushed down the road (again and again ::))
If nothing else my fitness is improving ;D ;D
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i was told mine was as well ran it in then i raced it at the dirt track nats 2010 and yes i niped it up twice but it still went took high spots off but i think it was gone by then
jim
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If its the same rotor on both the 74 & 75 models, you can use a 16mm bolt to remove it,thats basically all the genuine honda one is with a t'bar on the end. bang it off & check that key! I agree with the others,sounds like the timing's out, It's a bit hard to put the stator on upside down (180 deg out) with the stock wiring, as it's very short, allthough someone who came before you could have got creative,anythings possible & worth checking, Basic timing check in the honda owners manual says to remove the top stator bolt which reveals a timing mark scribed into the backing plate that should correspond to a mark on the cases,then to fine tune with a strobe light,18 deg BTDC @ 6000 rpm (bloody useless to you until you get it to run) The manual does'nt give static timing specs but i have a clymer manual which does,let me know & i will get it out for ya, I also agree with the worn out top end theory,have you ever had it apart & checked tolerances,some bikes feel o.k. through the kickstarter but are worn enough to cause hard starting,the kickstart gearing giving a false impression :)
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My bet is on a sheared woodruff key. Been there, had that. Good luck & cheers pancho.
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I agree with the others,sounds like the timing's out, It's a bit hard to put the stator on upside down (180 deg out) with the stock wiring, as it's very short, allthough someone who came before you could have got creative,anythings possible & worth checking,
SMED wins the cigar. Timing 180 degrees out.
Timing light shows firing on the bottom instead of at the top where the mark on the stator is. (Awesome tip there Pez ;) I would have been there for months trying to work it out. Static timing was perfect - that's what had me buggered)
So .... how do I fix that gurus ? :-\
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SMED wins the cigar. Timing 180 degrees out.
So .... how do I fix that gurus ? :-\
Have the crank pressed apart and get the big end pin bored on the opposite side of the crank.
Hope that helps ;D
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Thanks for the gem of wisdom Geoff ::) I was hoping for something slightly simpler ;D. I was thinking if I turned the bike upside down and set the timing again that could work ;D ;D
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Tony turn the stator 180 degrees :) or sell it and buy a KX 125 ;)
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Did that - and IT's ALIVE ;D ;D ;D ;D ;D ;D
Now just have to fix up the wiring :'(
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bugger - too late with an answer - had exactly the same problem with my CR250 T!!!
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So how did you fix it Rossco ?? Rotate the stator plate 180 and rewire it so it all goes together nicely ??
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I cannot take a bow for saying the timing was 180 out,that was lozza! But I'm happy you finally got the little beast to run, Can you just remove the windings from the base plate & swap them left for right & vice versa?
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I looked at that, but the coils seem to be solid with the mountings (?). The mountings are in quarters as well. The Yamaha coils are a separate thing, but these seem to be different. It still kinda works upside down, but the wires are all over the shop. Not a big issue really. I can still do the whole timing thing (now with the timing light 8) ) - it's just that it is on the bottom instead of the top. I'll see what Rossco comes back with.
Apologies to Lozza as well for selling him short ::) Should have read back further. You can share the cigar with him SMED ;D
Thanks for your help fellas. Saved me thousand of dollars worth of swearing ;D
The good news is I will have crank seals and all new bearings on the shelf to install in it when the time comes 8)