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1216 Rev limit


Ted M

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6 hours ago, jonny1bump said:

My crank snapped at 11K

Mine too! Ted: if you miss a gear, the engine easily over revs if you have an ECU with a too high limit. On my first 7/11, I used an ECU from an 88 750, missed a gear and split my crank. Use an ECU with a suitable rev limit. In your case, I'd go with any 1127/1157 ECU. 

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6 hours ago, Nik said:

Mine too! Ted: if you miss a gear, the engine easily over revs if you have an ECU with a too high limit. On my first 7/11, I used an ECU from an 88 750, missed a gear and split my crank. Use an ECU with a suitable rev limit. In your case, I'd go with any 1127/1157 ECU. 

Doesn't the 1157 ECU/CDI require a resistor in the ignition circuit or a Blandit 12 ignition switch to work?

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  • 2 weeks later...
On 2/2/2019 at 5:09 PM, Ted M said:

Many thanks for the replies I’ve got the blandit 1200 whirring loom and ECU so I should be ok

Be aware to use a bandit ignition lock, as the needed resistor is in the ignition lock.
If you do not want to, you have to add the resistor in the wiring to the ECU. ;)

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This thread made me think - which is always dangerous...

I made a comment on J1B's thread once, that I was surprised that forged big bore pistons were as heavy as they are, including gudgeon pin, 30/31 g heavier - that's 10 % heavier than standard ! - forces from acceleration/deceleration  increase to the square, so the extra force on the crank/bearings is double that of standard (brain's not as good as it was, but I think that's right) - it's surprising there aren't more problems, there must be many thousands of big bore oilers out there and not many problems. The standard tacho lies it's cock off at high revs though, that probably makes people change up earlier. If my  F = MA calculation is correct, the big bore piston extra force at the std rev limiter (true 10800), is like setting a std pistoned 1127/1157 limit to just over 11,300 revs - something like 12,800 on a standard tacho !!

I've got an amber change up light at  true 10,200 and a red one at 10,500, as said the power is dropping by then anyway. Would like to drop the piston assembly to standard weight though, then use a true 11,000 as a limit and all should safe - Suzuki built a decent safety margin in it seems.

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The stock limiter cut out is 10500. Red line of 11 on Suzuki tach is about 10200 in reality if I remember correctly.

I've been  revving mine to 11k for years and years at prolonged rpm and to be fair on a balanced and reworked crank that's been fine for me but certainly no more. 

But saying that on this latest rebuild have reduced it back to 10500 and see how curve looks next time it's on dyno before changing anything. 

I certainly would stick to 10500 on stock crank.

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I think the rev limiter was upped on the 1127R models, the 1052R didn't rev as high (as stock either model didn't rev out) -  the pistons of the 1052 and 1127 weigh the same, so extra force was added to 1127 cranks with the added revs. Took my big bore to 10,700 by accident, it was accelerating well in 3rd and I missed the change-up light, over revving would be a problem on track. The Wiseco pistons I used were very close in weight as a set at least, just too heavy, JE pistons are 2g lighter from their figures. Balancing will help, but dropping piston assembly weight would be a even more helpful for high revs and then get it all balanced. Haven't got a clue whose good though.

I've seen Wossner pistons that have a lighter design, I'm going to ask about their weight - they have tapered gudgeon pins too, which will drop weight. Wossner are well known in the car world, not so much with bikes though - anyone tried them ?

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On 2/11/2019 at 10:44 PM, jonny1bump said:

Yes heavily reworked, but to be fair it had a real hard life.

im not 100% sure about it but ive heard that the 59mm crank is a little weaker than the 58mm crank. but i hope that my 58mm will last a long time with 150 at the wheel and 11950 rpm limit

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