OzVMX Forum
Marque Remarks => Yamaha => Topic started by: Kane Mcguire on November 02, 2007, 07:48:03 pm
-
i have a really good 465 with dg pipe and boysen reeds. it revs well up top and has good power up there, but before that it has no pull. it has torque like a 250 i would guess but not at all like i remember 20 years ago. it will not pull torquey wheel stands through the gears, only if its well up in the revs. it seems to run ok jetting wise and compression, reeds, etc seem ok. please help! thanks.
-
you'll find the answer here ?
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&rd=1&item=180175982179&ssPageName=STRK:MESE:IT&ih=008
and thats very cheap advise :P
-
good advise freakshow you cant go wrong there, anyway your concern could be related to a number of things such as, jetting incorrect(possible blocked jets), not getting full throttle,exhaust blocked,gearing incorrect,compression and ignition timing,blocked air filter,rear brake lever jamming(on the clutch cover), air leaks at manifold, fuel mixture(eg 20:1), spark plug incorrect,hope this will help CHEERS BONEHEAD
-
Hi guys,
I am now the very proud owner of this beasty. Obviously Kane has sorted the thing out as it went like stink when I first got it home 8).
Slight problem now though :-\ It started to blubber and has got progressively worse over the last couple of rides - now it is really bad :o. Starts well and runs crisply on the pilot jet, but as soon as I give it some throttle it turns to crap.
I have bought a new iridium plug, tried fresh fuel, checked float level, cleaned carb, but all to no avail :(.
The only thing I haven't done is clean the air filter (I've bought a new one but haven't tried it yet) - would that do it ?? Doesn't look to be overly gummed up (but that's probably not an indication). I haven't been riding it in dusty conditions.
I did not take note of the jet sizes while I had the carby apart, but based on the fact that it went VERY nicely when I first got it I thought maybe jetting was not it. Will do so on the week-end.
Ideas ???
Otherwise I will ride it around blubbering (the bike and probably me too ;D) at CD6 until someone feels sorry for me and helps ;) :D
-
check all your wiring conections, cdi, HT coil mounts and the grounding wires if any YZ, the description could describe an earth going bad through corrossion at a mounting point or a loose terminal. Could be something entirely different but it doesn't cost anything to double check ;)
-
what the heck am I doing in the yamaha camp!!! :o ahhhhhhhhhh! runaway!!
-
throw the iridium plug as far as you can
they are shite
put in a standard b8es ngk
run it on 40 to 1 synthetic
with bp ultimate
oil and fit new air filter
set mixture screw to 1 and three quarters out
change plug cap (they are only cheap)
run it if it is still crap check plug colour
if its oily pull off carb
tell me what jets you have and check your needle jet and needle
are not worn
its one of those things a process of elimination
could be top coil stator timing broken wire etc etc
do what i said first and see how you go
cheers rusty ;D
-
You are a legend Rusty 8). Once I get it going you can show me how to ride it ;)
I will try this on the week-end and report back.
Shall also check electrical connections Doc - now get back over to the Yellow Peril room ;D ;D
Cheers
-
my YZ250h use to do the same thing
started ok allright down low but when you open her up it blubbers like shit...
replaced the inlet manifold....bang .... hey presto different bike... :)
-
Do you suspect was an air leak Andrew ??
There was a suspicious fuel mark on the side of the barrel where the model number / capacity is.
That is now gone - Is a pin hole there a possibility ? Would be very odd wouldn't it (?) That would not make it progressively worse either. I will have a closer look at the manifold (with my glasses on ::))
-
if it had a air leak it would do opposite
and lean and rev out ;D
-
i forgot something... i also replaced the reeds with new ones at the same time i
replaced the manifold...
-
DOH! forgot one critical thing. When I turn the fuel off and run it out it goes well again very briefly when running out.
-
if it had a air leak it would do opposite
and lean and rev out ;D
you are right there holeshot buddy..mine was reving out almost like missing a gear
but it sounded like it was running toooooo rich....
-
mmm..does sound like a fuel issue. Most bikes go really hard just as they run out of fuel as the mixture leans right out. If it revs well during this period then ignition is not the problem. I can only assume your airfilter is okay and yes, fit the new one if you have to eliminate this item :P ;D ok ok..back to the yellow men ::)
-
i had some trouble a while back with a needle jet that was "spun" slightly off line.
i must've had the carby off 10 times before i found it as it was only ever so slightly miss~aligned.
it would idle well but missed and blubered when reved.
CD6 on a 465 hey? very cool Tony 8)
-
Not with you on that one Mick ::). What's with the spinning of the needle ??
Don't worry I already have you on the list for a ride on it - if I can get it going properly. It's no beauty Queen, but is Mechanically very good. I will ride it as is for a while until I have the other restos I want to do done (250, 50, 125) then she will get the cosmetic makeover - not a lot to do - a bit of paint here and there, replate a few things and tidy up the tank.
Looks like the 250 is going to have to miss the trailer to CD6 as she won't be quite finished (thanks very much XYZ in USA >:( >:( >:( - has anyone had any luck with this absolute idiot ? I swear all I want to do is give him a few hundred US dollars and I still can't get him to talk to me. All he has to do is put the stuff in a box and go to the post office - how hard can it be ?) No side covers or decals. No manifold either. So close, yet so far off :'( :'(.
-
Just one other thing that i recently found to be an issuie on my yz250F where the inner magneto rotates it was rubbing on the wires from the stator coils and had wore a hole in them, I couldn't see this until i pulled off the rotor to do a bottom end rebuild all good now...
OLDYZMAN
-
Not with you on that one Mick ::). What's with the spinning of the needle ?
perhaps i didn't make myself clear enough Tony,
the "needle jet" not the needle.
basically it had rotated slightly and didn't work properly.
bugger.
a 465 hey... i'll have some bikes on the the ready too mate and you're more than welcome.
i should be there friday arvo~ish... :)
-
DOH! forgot one critical thing. When I turn the fuel off and run it out it goes well again very briefly when running out.
hmm yes that is a critical thing, when you cleaned the carb are you sure you got the float in and the float valve all back in the same way, sounds like they are leaking and she is over fueling, thats why when you drain the float bowl just before it runs out of gas it comes right. Judging by this being a deteriorating thing the floats may also be leaking or filling with fuel.
-
That's not a bad thought Marc. I have a YZ250H carb here. I think they are the same. I left my frickin' manual at home unfortunately :-\ so I'm not sure. I'll put them side by side. It will idle all day on the pilot - would that still indicate the floats filling up. Worth a try anyway
Anyway - fitted the new air filter. Put the needle back on the top clip (where it was originally when I got it) and got the following numbers for jets.
Slide - number 3 looks to be not worn at all
Needle - 6F18
Needle jet Q-2 (also has number 247 on it)
Main Jet 400
I was lazy and didn't measure the pilot 'cause I couldn't find a small screw driver and I think the pilot is about right ::)
What do you all reckon - should I bother putting the carb back together or go straight for a change of jets?.
If I had my manual here I would have more of an idea if they are right >:( - anyone got one handy?
-
Gday Tony , Clymer manual, for YZ465g
VM38ss
ID 3r500
Main 400
Needie jet Q.2
Pilet 50
Jet needle 6f16
Clip pos 2
float height 1.06 in 27 mm.
hope thats of some help, cheers KB.
-
You are a legend KB - is the 465G the same as the 465H ?
Looks like I've got most of the numbers right.
Hope the lotto tonight is the same ;)
I will put the carb back together and fire her up to see what happened.
I probably should do that so we can work out what the problem was anyway.
-
yeah it will idle all day because it can run a little rich at idle, but if it blubbers as soon as you snap the throttle that gives some indication that it is rich at idle.
swap to the 250 carb, with 400 main, it will be near enough to test it and it will eliminate the carb as the problem....my money is that it will go like hell with the 250 carb on it.
-
Heres the whole page ,might be of use,cheers(http://i39.tinypic.com/2cgfr80.jpg)
-
i,m having similar drama with mine ,i suspect it,s the reeds , boisen,s ,probably fatigued , will try stock reeds i think
-
does anyone know why the air jet is not mentioned in the specs (the one that sits on thew inside of the bell)
OLDYZMAN
-
it,s in the text of the manual , not in the chart
-
Gday IMS6201,
Can you tell me what is says in the manual for a yz250F 1979 about the air jet...
Brett
-
1.5 turns on pilot screw , 400 main, q/8 , 6f16 , 50 , clip pos 4 , ( pos 1 is the top )
-
Changed the main jet on the 465 carb to the 250 carb. That brings it up to spec with the 465G apart from the pilot (that I didn't check). Now has new air filter - guess what - the same thing happens >:(.
I beleive this bike still has boysen reeds - Is that my next port of call ?
Would I stick with boysen, go back to original or try the V Force (not legal on EVO I'd imagine :-\ )
-
i,m about to take mine out , i ,ve changed the reeds back to steel , i think the fiber reeds become fatigued and get a bit flappy , i,ll let u know
-
yep the std reeds worked for me ,
-
I'll give it a go and see what happens - hopefully the same as you ;D
Where would I get such a thing - the local Mr Yamaha ?
-
yep ,yamaha , if boisen,s have been fitted , the std reed stops are removed , so u would have to get those as well , if u don,t have a set , perhap,s just a new set of boisen,s ? i think one of the dt 400,s had an 8 petal block which fits , makes it a bit snappier i,ve heard , something i probably won,t get around to trying , would like to hear from someone who has
-
You've just made a decision for me. Thanks. I think it has boyeson's fitted so I won't be fitting the standards as I assume the reed stops are removed. Interesting as the reed block I have from the 250 has fibreglass reeds and the stops are still fitted :o :o
I was going to start a new thread in tech talk about the benefits of the boysens, but now that is academic ::)
-
well thats my guess down the toilet, but at least we eliminated the carb. Sounds like something started leaking or gradually breaking down over time...... back to the reeds and electrics I guess, crank seals ??
-
run it with the gas cap off.... fuel filter ????
-
For the dollars it's worth a try - I'll get a different one.
Fit new reeds on the week-end.
Come in Rusty - any more ideas ??
-
what,s the std gearing for 465 ? 14 to 46 ? i,ve got a 15 on the frount , reckn it was pulling well over 160 but bogging down a bit , also is the rear hub different from g to h
-
14 / 48 gearing is fine
carby you will need a 4.5 slide 390 main 55 pilot
fit your reeds and try
make sure float is not to high
if still no good
take off stator cover mark tdc on flywheel and case
set timing to specs i cant remember exact but get a dial guage
and set it btdc at right distance and mark case
get a battery and timing light start her up
check mark while engine running should be fluctuating at tdc at about 2000rpm approx
increase revs it should advance then as the revs increase a lot more it will retard slightly
this will tell you if your cdi is working ok
otherwise advance your timing plate about 2.0 mm
should be clockwise
these bikes are bulletproof and once they are set up
you can leave them alone for a long time
my 465 was one of the quickest in qld
it had dg pipe and muff
boost bottle, standard ports
was just set up good
cdi should be ok they are very reliable on 465s
not and air leak
does it have too many base or head gaskets some people put them in
to tame them down
try the timing and ride it you can always turn it back
keep me posted would like to know
cheers rusty ;D ;D
-
No sweat - thanks Rusty. I will gradually work through that list and order the parts today.
-
hi yz250h kane here. if the bike ran great previously then do not try different jetting. jets dont change all of a sudden! something has failed mechanically. if the bike runs good when you turn off the fuel tap (leaning out the mixture) then that rules out ignition problems. i would be trying needle and seat and the float level and also making sure the floats are not bent and rubbing the side of the carb bowl. also that the main jet hasnt fallen out etc. it has new boyesen reeds. but check they are sitting flat and not broken. contrary to the opinion of many in this forum i have never had trouble with boyesens. over the last 20 years, fitting a set is the first thing i have done to every bike. always gives more bottom end and makes them rev cleaner. one more thing, i wish i still owned it!
-
Gidday Kane,
Mate, it seems like we think alike. That's the reason I posted on here. In that last 12 months trying to get a 125H motor going I have learnt a bit and thought it was very odd that it should deteriorate over just a couple of hours.
Full credit to Rusty and everyone else for the advice. These are all things I will add to the list for checking. I guess that is what this thing is all about - sharing lessons learnt.
The key for me is that once I got it started wehn I first got it home (thanks for the excellent advice - I continue to use it) it went like the clappers (as you can attest).
Something I haven't stated on here already is that it won't just start straight up. I have worked out I need to kick it a few times with the plug in, pull the plug out and kick it by hand a few times. When you kick it then it will fire first time every time.
I have not pulled the reeds out yet. Hopefully I can use them for the 250 if they are still good on the 465.
I will try a few things next week-end and see how we go. I have ordered new jets to take her back to standard. Should it be altered for boysens ? By the time I'm finished I should have new air filter, all new jets and new reeds - wtf else could it be ?
Sorry mate - she will probably be with me till I kick the bucket now ::) I've got a bit of a tart up planned for her later on - similar standard to the 250.
thanks for chiming in. I will keep reporting back
-
kane , i hope u didn,t read into any of my posts and get the idea i didn,t like boisen reeds , that,s not the case , but it seems they do need to be kept fresh , for me the steel ones , i have on hand , are easier to live with , i,d like to give the dt400 ones a go , but am unsure which model fits
-
Has anyone mentioned crank seals... worth a thought .
-
Has anyone mentioned crank seals... worth a thought .
a second thought , thanks old fart , even though i,d replaced them on mine , i checked them , and found one had worked it,s way out some how , evo at dundowran park hearvy bay tomorrow, still not quite rite jetted but good enough to ride
-
sounds like an air leak to me, check your base gasket and for cracks in the cases near the base gasket.
do this BEFORE anything else!, I have lived and breathed these things for way too long and that is where I would go first.
-
Success - Installed the new reeds and we are back in Business. When I pulled the reed case out one of the reed screws was sitting loose on the intake. I think it was trapped there by the reed cage, but would have been disasterous if it had escaped. I have gone back to standard jetting apart from the 400 main ('cause the 390 hasn't arrived yet). I fiddle with it a bit as response of the bottom is a little flat. Pilot screw is out 1 and 3 quarter turns -I'll have a play with that.
So don't know if the reeds were fatigued or wether that loose screw had something to with it.
Now I just have to find a long enough straight to do a few chop tests - Can this be done in say third ??. Full throttle in top is getting pretty quick.
-
Can this be done in say third ??. Full throttle in top is getting pretty quick.
Pussy ;D ;D
-
good to see u have had some success , mine ran well for a further 10 seconds ,, how hard is it to bend a crank , or how easily are they to get mis alined ? sucked in the base gasket again , what is good for case sealant ? i,m going to re kit the engine and start again
-
good to see u have had some success , mine ran well for a further 10 seconds ,, how hard is it to bend a crank , or how easily are they to get mis alined ? sucked in the base gasket again , what is good for case sealant ? i,m going to re kit the engine and start again
Have a think about getting the cases machined matched with the barrel so that the base gasket has even pressure on it when torqued down. Check the studs in the cases for pulling out or stretched threads. Do a pressure test once you have the motor back together and if all is ok then you have a good place to start working through any other problems.
-
plug chops
full noise in 3rd is ok to do a plug chop.
cheers
jim
-
Good on you Jim. 3rd will make the whole thing slightly more civilised. Full noise in top is fairly moving and the last thing on my mind would be the chop test :o. Self preservation would be most important I think.
Bad luck lms :'( :'(. Any idea what the cause was ? Hope she comes back bigger and better. Threebond grey is the best sealant by all accounts.
-
me too , strip it down and start again , i did run it for one race , but barley controlable as it went from absolute blubbery to holeshot weapon when it got extra air intake boost , wonder if i can patent that ? will have to find the vibration as well , if that doesn,t work , i,ll drop a 490 in it
-
With the base gaskets being sucked in , i have "yamabonded' mine on the transfer port edges . The experts told me not too , but ever since I have done this , no issues. You must remember that it is a big compressor /piston moving a lot of air around , especially when dirt tracking.And a 465/490 is a great dirt track bike , set up right will outrun a 450 modern.
-
make your own base gaskets
make them about 2.0mm wider
around transfer edges ;)
you can also centre punch small holes on both surfaces :o ;)
-
rusty does the center popping apply to the crankcase ? does it help to hold the base gasket in place ? have been cutting my own gasket,s for ages , out of all the yams this one is the only one i,ve had problems with , and i,ve used miss matched cases ect , seem,s more care i put in , more problems, experienced ! must be some warping , torm 92 , i have used sealant on the base before , and it let go in no time , could be the vibration i,m trying to find , anyone got a good crank ? cheap
-
yeah you centre pop both surfaces
and cut your gasket like i said
and match up all inside edges
you can put non hardening permatex
on both sides of gasket i have
had a lot of success with it ;D ;)
-
yip yip , it now has torque (and everyingthing else) plus a bit more like it did a long time ago , hope it lasts , i suspect the sealant i first used on the crankcase halves started to fail , thanks everybody for the 3 bond advise , for the vibration problem , i made a set of heavier frount mounts and fitted a head stay ,i did have the crank professionally checked , it was within .003" but they got it to .001" well worth the $47 for peace of mind ,when i first assembled the engine the origional bearings seemed ok but were now a little loose , so new ones fitted, may have helped ,another set of new seals too , i fitted a 490j manifold and yeis can , , makes it a little more forgiving to jet , as for the base gasket problem , i bought a new wr one , they have a line of raised rubberey stuff on them , to help stop slippage i feel ,and a little 3 bond on the other side , genuine parts cost lots ,$33 , torwards the end of the session it did start to play up down low , on checking it would have had less than a litre of fuel in it when this happened so i think low fuel pressure , the cylinder has had extensive porting and is very smooth in the transfers and ex , intake looks to have been lowered , 490 dg pipe , 2mm os , big jets, 6f16 / r0, 40 pilot, main is 440 very crisp or 450 to richen it a bit for lots of wide open running , now all i gotta do is get it to stop ! i tried a champion n3c plug in one of the 490,s last week , first time ever started first kick , and it stopped 90% of pinging , which worries me ,