1998 with backfire issue
 

Hey guys,

First off want to say great source of info here!!!!!

So I took the plunge and picked up a 98 supercock,

I have just put on the plate, took her for a 30 mile romp

I am finding that she is spitting and backfiring on the front cylinder only, or so it seems. The backfire is only when under no load and at any speed any rpm. if I am running 3k or 6k she will spit but only when steady, if I get on it she runs strong.

I am going to have the carbs checked for sync, jet kit installed by previous owner. but wondering if it could be the cam chain tensioner???

there is 24k on the odo.

The former owner installed the easy on in the rear cyl, need to do the front one.

Just wondering if this could be the answer??

Thanks all for your help,

Mike

Greetings

Check out the exhaust headers and gaskets for a solid seal. Also the seals to the muffler connector pipes. These might differ if you have after-market pipes fitted but you'll still need a good fit to eliminate pesky air leaks.

http://fiche.ronayers.com/Index.cfm/.../Group/MUFFLER

Post some pics of your stormbeastie!

welcome to the forum and i am with WICKY on the exhaust donuts to check first. i never had a problem until i removed the stock mufflers and muck one up. i get the backfire too just haven't gotten around to change the donuts yet. +1 on pics.

Thanks for the welcome guys!!!

I just did some investigating,

Seems the former owner was a member here, let me quote his post and what he failed to mention when I went to buy the bike.
so now I think I know what I have, I can only hope he will answer to my message and I can find out what was or was not done

:confused: guess its just my luck

So it sounds like you need to check the valve timing first thing. What a joy....

Nice. There's integrity, lol-- and when that's lacking, some people at least have the common sense to know that they should disclose any issues if their crap is posted on a forum somewhere. Geez..

Either way, hopefully not too much work and you'll be ship-shape! The bird is worth the effort IMO. :)

I am going to open the lids this weekend, but for now I am letting the bike do the talking

seems even though there was the timing issue, it may be a fuel related issue I am having now. The symptoms are becoming more pronounced as i put a few more miles on her.

seems like the front cyl is starved for fuel, then it pops like an incomplete combustion and I need to bring up the revs to clear the motor and get fuel back to the motor

stuck float maybe, fuel pump, tps ??? time to troubleshoot

I agree, do the easy stuff first.

Have you done a compression test yet? Easy to do, and it might tell you something before you start pulling parts.

Oh, and Welcome. I hope you get it running well soon. This bike is the most fun I've ever had on 2 wheels.

Hey surfer,

As in my other post, thanks for the insight, going to start with the carbs!!!!

from what I understand Yamaha makes a water born/based carb cleaner that rivals anythin on the market, give me a tall one!!

Going to be a carb cleaning fool this weekend!!!

thanks again

Mike

ok update on situation

so I dug into the hawk tonight, pulled tank, off with the 5 hoses, pulled airbox and viola

here are the carbs all up 40 min to uncover the carbs not bad for the first time.

I took the carbs off, interesting that the pair valve mod not done but the tps was done hmmm??

so i pull the carbs

turned them over and noticed carbon trails in both that stop at the butterfly's

looks like a lot of low speed backfires again hmmm??

so i did a quick clean, changed the low end jets to 50s from 45s

as per my low end fart, starving for fuel.

while inside i flipped the p.v. and removed all associated parts, crimped the hoses over and put it back together.

ran it a mile down the road and fart pop she seems to totally starve for fuel

let it sit and she goes again

I am going to open up go back to the orig. setting and start over.

any ideas? as of now the primary jet is 182 f and 185 r 50 on the low jet and not sure of needle slash shim settings, has d&d slip ons

going to rip into it tomorrow afternoon

Hey All,

hope you are all out enjoying these last few good riding days before winter sets in!!


so I went back to the orig. starting point, then set the pilots to 2.25 out

all back together and the pop is there from 2500 to 4000 +/-

I came home, and sit here looking at the carbs, there is a carbon trail up the inside of the carbs that stops at the butterfly's same on both.

this would tell me the exhaust valves are letting the pop back into the carbs??? or am i missing something

I have not synced the carbs yet (have to buy/make the tool)

but I did remove the the valve cover from the rear and inspect the timing.

should I be able to pull slack between the cam gears? very slight but chain sags about 2 to 4 mm very noticeable.

thanks guys

So what is this thing call "winter" that you are talking about?? Sorry couldn't help myself.....lol That is the main reason to put up with all the BS here in CA, year round riding. In fact it is just now getting good ;)

So does it pop all the time, only on deceleration or acceleration. It could be the pair system, if it is still hooked up or a bit lean on the bottom which is a pilot jet issue.

How bad is it? I think it really is a non issue as I seen that condition on a few bikes. Just clean them real good and see if or how long it takes for it to come back.

This is the first thing you have to do. These bikes really do run like shite when they are out of sync. It also should be checked from time to time. But after you have had the bike for a while you will be able to feel if they go out of sync.


Yes there is a small amount of slack in the cam chain so no worries there.

as i line up rt mark on inspection port the ri and re marks do not line up, seems they are about 1 tooth off it seems the intake gear is 1 tooth retarded or to the rear of the bike

could this be the answer, i have to run out now and i am coming back in a few to do more investiating

If your exhaust valves are letting flames come up through your carbs, you have a real problem.

The "carb farts" are going to happen occasionally with the VTR. It's backfiring up through the open intake valves.

And the 50 pilots may be a little large. I remember another member going to 50s, then dropping down to 48s.

Also, make sure you didn't hook up the vacuum line to the petcock wrong. It's a common mistake when you remove the tank for the first time. It goes on the side port of the petcock, not the bottom, which is a vent for the diaphragm.

See I am getting old, I didn't even see the comment on the #50 pilots......
Those are a bit large and I would swap them out for something smaller. I like how the #48s work and others have had good luck with the #45.

I am back to the 45 pilot and still getting the backfire as of this morning,

lol i did have the vacuum line on the wrong spot on the petcock

i just need to dig deeper,

would it be stupid to think maybe the cam chain stretched?? somethings weird about mine, i can push the chain down onto the gears when its at rest the chan seems to ride up on the gears.

so I loosened the jam nut on the rear cct, found it to be 1.5 turns loose from hand tight, tightened it to hand tight 1.5 turns and 1/4 turn more cold. I checked the timing and everything lined up on the rear cyl. so if the timing is on the fart is most likley a jetting / tps related issue


i did notice something on the way to work this morning.

I noticed that since it was a bit cool out I choked the bike, no carb fart! as long as the choke was pulled out i had no 2500 to 4000 pop / kick. i pushed the choke in half way and still no backfires, pushed all the way in and pop/kick right away.

so this means i am running lean????...

Yes it does.

Have you checked your carb diaphragms?

Surfer,

I did check the diaphragms, both the bikes and wifes LOL

but all joking aside they were a bit dirty with a slightly gooey feel (the ones on the bike)

I cleaned them up, set needles at slot prior to last and checked for ease of slide.

maybe go to 48 slo jet from the 45 thats installed now and shim up the needle one shim, of course i am balancing the carbs tonight prior to anything else

OK,

once again the tank is off, I am going to put in the 50 slo jets, pull the needles and shim them back 1 shim each side on the 2nd from last notch

set the pilot screws 2.5 turns, i am at 2 1/4 turns out now.

if she keeps popping I have to believe its a bad valve

I dont have the insert to do a compression test, damn kit has the 2 bigger plug inserts from working on boats.

will have to invest in one soon..... like tomorrow lol

I would hope this at least stopps the pop, I need to get a pair of 48 slo jets since the factory kit included the 50's thats what will be going in.

I am breaking the troubleshooting law by adjusting more than one thing at a time but since 90% of the posts here on carb issues all use the same set up I will go with the masses and adjust up or down from there

I vote check the PAIR valves. Flip the reeds around to shut them off, if it hasn't been done.

hey scoober

pair was done by po but i completed it and capped covers with rubber hose vacuum cap.


I do however keep referring back to the search (carb issue) I realize that I am a moron lol self diagnosis

hmm a k&n air filter = lots of AIR, p
PO compensates by setting needles back as far as possible!!

K&N = very lean condition with his setup and throwing a ton of fuel at the problem from what I read is not the answer

I have pushed the needles in, 2nd clip from taper, jets set as previously described and will know how she runs on my way to work tomorrow o and 2.5 turns open,

balancing the carbs in about 10 seconds, lol getting grease all over the keys

AAAAAAAAAGGGGRRRRRRHHHHHHHHH

I just can't seem to win,

I get her all set, take a 1 mile loop to warm her up and balance carbs

get back to the garage and hey look at that

aunt e freeze has decided to show up (i hate when she comes out!!)

damn coolant leak from I believe the carb line, just another F%$IN headache

Gave up for the night, have to steal the wifes jeep to get to work, I hate driving!! lol

compression test complete your results are in,

YOU MY F?RIEND ARE SCREWED

found 125 on front cyl and 150 on rear

HELP!!!!!!!

any ideas???????

I feel bad :(
Don't give up!

ok, been a few days, the super hawk is open,

took off front head, found ex valves to be a very light tan color and lots of carbon in the seats.

took rear head off to compare and viola no carbon in the ex valve seats.

I am concerned though, carbon this thick would be most likely from oil entering the combustion chamber, if this is so where is it coming from???

I am hoping that the oil is from valve guide seals 25k on bike

so I am happy finding my compression issue, once I have the heads clean and new valves lapped in ind all put back and timing back in order it will be back to jetting for slip on pipes, balance the carbs, and hopefully I have no more spit pop

phew

Simply, NO! The po had a cct issue and it's extremely rare that you visit that place without bent valves. It also sounds like it's out of time with the chains or it may have stretched a chain when the engine grenaded last. The carbon in the seat and carb is your clue - The valve not closing during combustion. You should park the bike until you get this sorted because the more you ride it the worse it's going to get.

:iagree:

Those valves needs to be replaced... And just as nuhawk said, the cam chain is likely to be stretched from the blow-up...

ok guys to just clear up a few things, The bike is down to the jugs, not going anywhere!!

from what I can see, the front head did not experience a cct failure it was never touched, still had the stock cct and all stock valve shims

the rear head suffered damage from a cct failure and was rebuilt, new valves, new shims, an ape cct and very minor carbon buildup.

this in mind lets ask why is the carbon so built up on the front but not the rear?
since its a known issue with the cct, and improper care (not changing the oil!!) would speed up this issue i would have to believe he cheaped out and only did the rear head.

its completey plausable that the thinned out old oil would also slip past the seals and get down to the front cyl to build up the carbon.

yes the rear cam chain may have stretched from the cct fail, but if the front has not failed then the cam chain would only have normal ware and tear on it since they are completly seperate.

I had low compression on the front cyl that was not damaged.

this makes me believe that both front and rear were close to 125 psi, then a rear cct fail and rebuild of that rear head brought the compression up to 150 with new valves lapped in.

then since he did not do the front the difference in compression would have the carbs out of sync and would create a difference in vacuum to pull in new air/fuel and lead to my pop spit backfire.

with this said I have decided to do new cam chains, new valves, 2 new ape cct's and possibly have the valve guides bushed by a local machine shop. this will make certian that i have the same wear on the top end.

while I have worked on many motors, from boats to quads to whatever,

it has been a while since I have had a street bike torn down this far!!

after owning 20+ street and enduro bikes this is the first time I have ever had this trouble, not to bad considering.