I NEED HELP!

[Carterc]

i dont know what he said, it might have been BS for all i know. and what would i do if i put super pump gas in it and it pings or knocks and im still at the pump? lol

[Carterc]

also i dont know how to adjust "some stuff" im new to bikes and know nothing about engines 

[Mark Olson]

well it sounds like you need a manual and some local help from a fj'er in your area.

most of us will work for beer 

somebody in your area might come to your rescue.

[Flying Scotsman]

She is sweet looking.I wish I was close so I could try her out.A compresion gauge from the auto parts store would help tell you what gas to run.Cost you about $40.
Nice bike and easy to work on get those hands dirty.

[andyb]

I don't know this stuff all that well, but is it not possible to run high compression pistons with normal/ slightly advanced timing on pump gas -even high octane pump gas?  Does it depend on how high the compression is for the piston in question?

Dan, it depends on the compression.  If you were tuning it to run exclusively on alcohol (ethanol or methanol, but excluding E85), it wouldn't be surprising to aim for a static compression around 15-17.0:1.  Running gasoline, even as a mix, in an engine built to that spec is going to end badly.  The highest octane fuel that I can think of is VP Import, which runs around 120, approximately comparable to methanol.  The other side is that the stoch ratio is vastly different, and I'd be suprised if it ran at all on the "wrong" fuel.  Burn rates and flame propogation are going to be different also (and the FJ does not have a remotely efficent chamber for a racing use), so that'll move the timing around as well.  However, most of this is moot because we'd be talking about very custom pistons, and they'd be expensive to the point of silly.  Most likely it's got wiseco 77 or 81mm pistons in it, because they're fairly cheap and easy to get.  If it's got the 12:1 77's in it, it'll work on really good pump fuel, but it'll do better with a thicker head gasket to bring compression down, as there's a chance of overheating at idle in a Texas summer. 

I'd guess that there isn't anything particularly exotic about the engine, for a couple of reasons.  The pipe isn't a sidewinder, and there's stickers on the swingarm.  That would lead me to guess that the prior owner didn't remove an extended swingarm for sale seperately (because that'd have the stickers instead).  It's possible that he swapped pipes, but not hugely likely imo.  I'd guess that we're probably talking about a pretty typical engine that could even still have stock pistons.

But if it's got "race gas" in it and unused switches on it... my guess is that the prior owner ran nitrous on it and used a high octane fuel to help eliminate detonation at the track.  If he drove it as a daily/weekend ride, it'll probably do just fine on pump gas, possibly requiring 91+ if it's got the typical 10.25:1 pistons and aggressive cam timing in it.  I'll wager then also that it doesn't have advanced ignition timing, as that'd be a problem while on the bottle.

As before, a compression test will easily give you a ballpark idea of where it's at, popping the oil pan off to clean the oil strainer is a good idea (drag launches can chew up clutches, and that material has to go somewhere), and popping the valve cover off to see what cams/sprockets are involved will all be good ideas.  Odds are it needs new valve cover bolt grommets anyhow

[racerman_27410]

First a compression test to know for sure what you have would be just as good if not better (the PO may not remember all the details.)

If it is high compression .... octane booster added to premium fuel can get your thru until if/when you want to shim the head gasket.

KOokaloo!

[Travis398]

Okay I'll bite, what number on the gauge is too much for pump gas?

[andyb]

Okay I'll bite, what number on the gauge is too much for pump gas?

When it detonates   But when you're utterly blind as to what's in the engine in the first place, it'll give you some idea.  If the gauge reads say, 230psi, I'd start with a good 110 and see what happens.  It's only one piece of the puzzle.

Having an idea of what cams are in it and where they're timed also plays a role though, as you can bring them together and bleed off cranking pressure... and then get detonation at higher revs.  Usually those motors are really peaky though.  

[fj1250]

ON the positive side, It's almost impossible to find pistons for the FJ with higher than 10.25:1 compression ratio.
Even if the cylinder head has been decked as much as .030" and the cylinder milled to bring the pistons up it's unlikely you'll need anything more than 93 octane pump gas. Now how it was jetted... to run on race fuel? It's ususlly recommended that the jetting be richened up for race fuel. Rich is ALWAYS safer to start  with as your unlikely to have engine damage occur.  A fouled spark plug is cheap compared to a detonated piston.
Also remember, that if it does have race cams, compression levels at cranking speed may still be in the normal to low side.
A good running Legends car is designed to pump 180 p.s.i  which 600 racing claims is 10:1 compression ratio.

MC

[fj1250]

Oh yeah, just because it has race gas in the tank doesn't mean it needs race gas.
Some people like to smell fast.
The bike isn';t stretched and lowered, Probably has stock carbs.
Quite likely a stock bike in wolf's clothing.

MC

[moparman70]

hey its gots lots of stickers it must be fast... seriously though ... I can't tell but the exhaust doesn't look too modified which is a very important part of the power ... I am with Andy along that lines maybe due to the exhaust being what it is it is not highly modified.

[Pat Conlon]

".... It's almost impossible to find pistons for the FJ with higher than 10.25:1 compression ratio.

Mike, didn't Wiseco make some 77mm pistons that were 12:1? Those along with a head shave and advanced timing.....
I agree with the Andy:
1) Disregard any advice given at the Harley shop, their strong suite is not FJ's
2) Contact the PO for a full description and advice.
    He made it run fast so he know's what he is doing, probably. Wonder why he sold it? Traded it in at a Harley stealership? Naaa
3) If unable to contact the PO, do a compression check. Heck do it anyway.
4) You're *probably ok* with 91/93 octane gas if the PO used it for his daily commuter.

Worst case: You would have to add 1/3 can of octane booster every time you get gas, until you could get into the motor to lower the compression and/or retard the timing.

Yea good point: I wonder if the PO got paid for all those stickers?

[Carterc]

alright guys, i appreciate all the help! So its the general consensus that i should get a compression test done, which would tell me what exactly? and it would most likely be "ok" to use the highest octane pump fuel, which could at worst do what exactly?

keep in mind that i have no idea what you guys are talking about but i have google on my side and ive learned way too much from this post haha.
keep it semi-simple please.

Thanks again!

[racerman_27410]

my 1349 motor has 10:25 compression pumping 200 PSI....... runs great on pump gas.   


KOokaloo!

[Flying Scotsman]

Good to know,what octane 93.