need suggestions- 426 smokes on cold start after new piston



9 replies to this topic
  • MikeOK

Posted January 20, 2002 - 01:30 PM

#1

I put a new Wiseco in my 426 last week, used the 13.5:1. I've ridden it several times and it runs great, better than stock even. I was running some bean oil in the fuel the first couple tanks so I thought that was causing the smoke, but today I used straight 93 and on a cold start it smokes. It doesn't smoke right at start up but after maybe 30 seconds, then for maybe a minute, then everything is fine (I experimented off and on all day). I can re-start after it has set for 30 minutes or so or less, no smoke. But let it sit for more than an hour and it smokes like a Banshee hehe. One thing to note, the oil rings seemed very tight when I put them in. The other rings were fine, and the cylinder had slight vertical lines but very slight. I have maybe 5 hours on it so far and I have checked the oil religiously, no oil usage that I can tell (one oil change in there). I promised my son a trail ride tomorrow but after that it's coming back apart and I would appreciate any suggestions you might have. Thanks in advance...
Mike

  • Taffy

Posted January 21, 2002 - 12:35 AM

#2

this'll be something to do with your oil ring i think. if it's siezing at the beginning and then freeing under expansion that would possibly be your answer.

i'd have a word with the importer/tech division etc.

Taffy

  • SFO

Posted January 21, 2002 - 06:03 AM

#3

The wiseco rings aree a bit of a bitc* to install compared to stock.
Personally I index the gaps with the wirist pin, 180 degrees apart instead of the recommended 120.
I used a 13.5-1 piston too and have had no problems.
Tell us what you find when you pull it down.

  • MikeOK

Posted January 21, 2002 - 12:07 PM

#4

Thanks guys- I tore it aprt today and checked the end gaps, the top 2 were good but the oil ring sliders were almost double the stock limit. I check the stockers and they were still in spec. Also, the gaps were not 180o when I took the cylinder off, the were more like 20o. I know I didn't put them in like that. I am thinking I might put the stock oil ring sliders since they spec way better, any thoughts? I mic'ed them and they are the same size except for ring end gap. Also, do any of you know where I can get the base cylinder gasket alone? I tore it taking it apart and wasn't really wanting to spring for the $35 Cometic kit unless I have to. Thanks again...

  • SFO

Posted January 21, 2002 - 12:44 PM

#5

Do Not Put stock rings on a wiseco piston.
Use the wiseco specs for ring end gap.
I like the cometic base gasket vs stock because its .015" thinner.

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  • Taffy

Posted January 21, 2002 - 12:56 PM

#6

repair the gasket!

we use hylomar over here or "how's ya ma!" as we call it. give it some!

maybe yanks know what you mean by 180o and 20o but i don't, so run that by me again.

you shouldn't use a thinner base gasket unless you've checked the squish clearance ( the gap twixt head and piston sir!).

as for the rings they must measure the same height, the same depth and the ring gap isn't the be all and end all. you can run the ring gap down to .010" and you measure this by putting the ring in the barrel on it's own and measure it with a feeler guage.

look at both pistons and see how the oil feeds up through the back (underneath). how many holes and how big?

Taffy

  • MikeOK

Posted January 21, 2002 - 04:27 PM

#7

Taf- I mean the oil ring gaps are installed 180 degrees from each other, meaning one on one side and the other on the opposite side. I guess this gives the oil less of a chance to get into the cylinder.

SFO- the wiseco gaps were .038 and the stockers were .018. More than double the difference. The top two ring gaps were actually tighter than stock.

  • MikeOK

Posted January 21, 2002 - 04:31 PM

#8

Taf- I mean the oil ring gaps are installed 180 degrees from each other, meaning one on one side and the other on the opposite side. I guess this gives the oil less of a chance to get into the cylinder.

SFO- the wiseco gaps were .038 and the stockers were .018. More than double the difference. The top two ring gaps were actually tighter than stock.

  • Taffy

Posted January 21, 2002 - 11:10 PM

#9

gotcha now!

first of all the rings rotate at about one turn per minute! so forget all that 180d stuff coz it lasts about 3 seconds.

the ring gap is poor but still ok and won't be your problem. you could ask wiseco what the spec is though.

your real problem is the ring sticking. check the top of the piston for detonation or anything missing from the piston. it will look like it was shot blasted. look for splatter on the cylinder wall like spraying grey primar with no thinners (orange peel finish to you!).

before you try it again use your nail file ( i know you've got one!) and clean upthe groove a little.

if the feed holes at the back are the same and the ring is no smaller or bigger you can try swopping them.

it's a chance that this will cure it.

also check that there is no correct way up for the rings. on cars they still have it but it's rarer on bikes.

sometimes you'll see the word "top2 printed on the ring.

Taffy

  • MikeOK

Posted January 22, 2002 - 05:26 PM

#10

hey taff how much is a tidgy bit?




 
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