1127 top speed

[Blue]

What top speed do you think an 1127 with 38’s would achieve realistically?  I’ve got the chance to put it on a dyno locally before I get it on the road but the dyno guy says his machine go’s upto 150mph! 

[canamant]

I'd recheck with the dynamometer operator.  Dynamometers measure torque and then convert it to bhp.  It does this by recording torque, engine rpm, and dyno rpm and then doing some sums. It "knows" what the overall gearing between the crank and the drum is because it gets a tacho signal from the engine ignition system and a signal from its own roller/drum. If the roller is limited to 150mph  then the operator only has to ensure he uses a gear which will not exceed the drum maximum.  In the past I've had runs in several gears with always the same torque/[power within experimental error.  I would expect your dynamometer operator to know the limitations of his instrument.  Perhaps he just wants to know what gear to run it in, but he should be experienced in these things.

 

[bluedog59]

If you want to do a worthwhile session on the dyno, get them to do it against rpm rather than road speed. I find you get so much more info when the printout shows bhp/rpm, bhp/road speed is only useful for waving down the pub and knowing your bike would do 200mph down bullshit hill.  

[Blue]

Thanks, he normally runs can I say ahem scooters on it! He pointed to the speedo on the machine which went upto 150mph & asked me what the top speed would be. It’s more about making sure my carbs have the right jets etc

Edited April 8, 2018 by Blue

[VJ]

2nd/3rd gear should fuel the same as 5th so id run it them.

 

Actually id wait to see what the dyno bloke did as a gauge of his skill first then suggest a lower gear if he has issues.

[Blue]

Sounds like a plan, cheers

[Gixer1460]

2 hours ago, VJ said:

2nd/3rd gear should fuel the same as 5th so id run it them.

Actually id wait to see what the dyno bloke did as a gauge of his skill first then suggest a lower gear if he has issues.

Yes and no LOL! It sounds like the guy uses a plain inertia dyno that isn't braked, so if the lower gears are used the load on engine is quite reduced and acceleration of the drum excessive to get reliable results. On 1100's, 5th will probably overspeed the roller, hence the concern - 4th should be safe on roller speed and allow sufficient resistance to load the engine and slow its rev rise - most of the dyno's i've ever used like using 4th gear especially if they use electrical braking to add extra load.

[Dezza]

I was at Bruningthorpe proving ground in 1989 once, and a just-run-in stock 1100K did something like 162 through the timing lights. The only bike faster on the day was a fully faired Spondon 1100 slabside, which likely weighed about 30kg less than the stock bike (dunno about the engine). This is the only way you will really find the answer to 'how fast does it go mister?" My Harris- no faring and undergeared - did 149. Same as the stock bike which is understandable as it had stock gearing at the time. It pulls much higher gearing as it weighs several tonnes less than a stock bike, but I do not know the answer to this all important question as it hasn't been measured in real, field conditions.

[cregnybaa]

Michael Dunlop's mega expensive oil cooled XR69 goes through the Sulby speed trap at 171 ish mph and that bike would want for nothing.

[Dezza]

13 hours ago, cregnybaa said:

Michael Dunlop's mega expensive oil cooled XR69 goes through the Sulby speed trap at 171 ish mph and that bike would want for nothing.

What is the engine though? It doesn't even have an engine number on the cases, at least the one I saw at Stafford didn't, even though I am guessing it should have an engine based on an 1100 slabside.

An xr69 has an aircooled engine though doesn't it? So it's an xr69 looky-likely, with a gsxr (??) engine........

Edited April 11, 2018 by Dezza

[Madb]

8 hours ago, Dezza said:

An xr69 has an aircooled engine though doesn't it? So it's an xr69 looky-likely, with a gsxr (??) engine........

@dezza yes and yes. It's within the spirit of the rules. supposingly output of 180bhp+. Nice,(read on the net somewhere) but i stand corrected if it's way out.

[dupersunc]

The Dunlop bike engine is based on a set of brand new 1127 cases which are still available from Suzuki. Hence the lack of numbers.

1216cc with a Nova 6 speed box. 165ish bhp.

Lovely thing.

[Dezza]

Yes, it is a really wonderfully built bike. I was admiring it at Stafford and was wondering what coating they'd used on the cam cover (as you do). The detail on the machine is top notch.

I'd like to know how much the Dunlop bike weighs - Steve Burns's Mission Improbable Spondon slabside in 1989 apparently put out 165 bhp and went through a speed trap at Bruntingthorpe at 183 mph, but that does have a 2 mile straight.