Just finished up CW big bore install, questions...

Ok, after some teething problems everything is done and it started right up and runs fine Wooo Hooo.

The "teething problem" was caused by borrowing an old beam style torque wrench from my neighbor, he swore it was accurate. Well after getting everything together when I started it up I noticed antifreeze leaking from the engine bottom left side. I knew right away what it was, ran to Auto zone and picked up a new torque wrench and took everything apart to re-torque the head. Sure enough the second time was the charm...

Now, do you guys think I could have screwed something up with improper torque setting the first time? I only ran it a few minutes before noticing the leak. I did loosen all the head bolts completely just to make sure before I restarted the torquing procedure. Looking at the oil there is no milkiness and the antifreeze is clear.

Second question, I only ran it for 10 minutes before it started to rain and I didn't notice any dramatic improvement in performance. I'm guessing the motor is still tight so I'm not getting nervous till I hit 300 miles or so.

Do I need to re-jet on a big bore install? Could that be it? I could easily raise the needle jet one notch.

Thanks for all your help....

Ron W.

time will tell if there are any leaking issues, just keep a watchful eye on coolant and engine oil colour..and external leaks of course..

If it is jetted correctly for stock displacement, leave the needle setting as is and go down 2 sizes in the main jet and you should be sweet..

maybe list the type of carb fitted,riding altitude,open or corked pipe? and current jetting if you wish confirmation.... :)

Edited by Craigo 485sm

time will tell if there are any leaking issues, just keep a watchful eye on coolant and engine oil colour..and external leaks of course..

If it is jetted correctly for stock displacement, leave the needle setting as is and go down 2 sizes in the main jet and you should be sweet..

maybe list the type of carb fitted,riding altitude,open or corked pipe? and current jetting if you wish confirmation.... :)

It was 5 years ago when I did the rejet total memory flop when it comes to remembering what I did, that's why I was hoping for a easy peezy needle jet adjust:-)

I'm running an FMF Power Bomb header and Q4 muffler, Mikuni carb and I think it was a dyno jet kit?

Thanks

Ron W.

It was 5 years ago when I did the rejet total memory flop when it comes to remembering what I did, that's why I was hoping for a easy peezy needle jet adjust:-)

I'm running an FMF Power Bomb header and Q4 muffler, Mikuni carb and I think it was a dyno jet kit?

Thanks

Ron W.

 

Being the "attention to detail" Ron W we all know ...lol...my bet is that it is jetted correctly for stock displacement... :worthy:

 

your coming into winter there ....if you want to be lazy, just see how it runs at WOT, if seems ok just leave it as is ....

But if you have some spare time I would drop the main jet 2 sizes..... :applause:   :thumbsup:

Being the "attention to detail" Ron W we all know ...lol...my bet is that it is jetted correctly for stock displacement... :worthy:

 

your coming into winter there ....if you want to be lazy, just see how it runs at WOT, if seems ok just leave it as is ....

But if you have some spare time I would drop the main jet 2 sizes..... :applause:   :thumbsup:

Craig,

When you say drop the main down 2 sizes don't you mean up?, for example the main that's in there now is a 150 shouldn't I look at installing a 155 or 160 that came with the kit.

Thanks

Ron W

Craig,

When you say drop the main down 2 sizes don't you mean up?, for example the main that's in there now is a 150 shouldn't I look at installing a 155 or 160 that came with the kit.

Thanks

Ron W

Usually you lean out the jetting with the big bore. My upstanding is that increasing the bore is like adding bigger lungs to the motor. I was running a 160 main in my fcr, yosh ti 400. After the big bore I went to a 158 mj and probably could run a 155 but I find the decel popping annoying.

Usually you lean out the jetting with the big bore. My upstanding is that increasing the bore is like adding bigger lungs to the motor. I was running a 160 main in my fcr, yosh ti 400. After the big bore I went to a 158 mj and probably could run a 155 but I find the decel popping annoying.

The more air an engine can take in, the more fuel it'll need. I stand corrected, didn't consider the effect of increased vacuum created by the larger bore thru the carb.

Edited by bmwpowere36m3

Craig,

When you say drop the main down 2 sizes don't you mean up?, for example the main that's in there now is a 150 shouldn't I look at installing a 155 or 160 that came with the kit.

Thanks

Ron W

 

 

I does sound odd  ....  but the bigger piston sucks more fuel from a smaller jet size , so you need to downsize the main jet... :thumbsup:

Needle setting doesn't usually vary enough to be of concern....

Correcto. It is called "signal strength".  The larger bore draws more air thru the same size carb results in more signal on the fuel jet.  So, yes - big bore kits run with 1 or 2 sizes smaller main jet.  

Yea , up in bore size down in main jet size .

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