Forum

[Waltr]

So it does sound like a well designed German forged piston in a well done bore would help the run-in process. There a few on this side of the pond that believe (by close inspection) the stock piston is less that perfectly round.
As far as the higher compression I don't consider a true 8.5 or 9.0 to 1 HIGH compression.

[Bullet Whisperer]

Pistons are not usually 'perfectly round', but oval, with the larger diameter running fore and aft. I regard 9:1 as a figure to aim for when tuning 500 Bullets, but usually combined with other modifications, especially cams and valve timings, to suit. Regards, Paul.

[jefrs]

Gosh, are you going racing? A stock DBD34 Gold Star was only 8.75:1 and some were lowered to 7.8:1. The EFI is a long stroke and there are problems with hitting the valves if you go over 9.5 so be careful there, you won't actually gain a lot more grunt.



1) What compression does is push the molecules closer together to decrease the flame path distance, which can make complete ignition faster, but with modern fuels is hardly necessary. The hot expanding gases then push the piston down the bore. We suck 500cc in and what ever that can expand to when heated up is the amount of shove you get; it's the expansion not the explosion that drives the piston, a good explosion will blow a hole in the crown. To get more power we have to burn more fuel more quickly, hence using higher revs, or a bigger engine. The EFI has a 5500rpm rev limiter and a heavy flywheel, so it rarely gets above 5000. It really doesn't like revving all that fast. It's useful fun torque power is in the mid-range. And that's how this bike is best used.

Doing this sort of thing is for racing, and you can end up with a grenade motor.

If you can get 34bhp out of it you're into Velocette Venom territory, but with more torque; it is still not going to be fast by modern standards. There are other, better ways of getting more grunt than high-comp pistons on this motor; free-flow, mapping, valves. If you go very high-comp, you will probably need to change the crank and con-rod too.



2) I had an electrical ignition fault, missing that made the plug and top end soot up. I cleaned up the soot but the oil had turned black, so there is some blow-by at the piston, this is normal on any motor. It took two oil changes to get rid of the soot inside the engine but the oil has stayed clean since. Hence the stock piston is fairly good or the oil would have turned black again (like it does on a diesel car engine).



If it ain't bust, don't fix it.

[Tim NZ]

One of the reasons behind the 5500 rev limit is due to the std ex valve being prone to getting its head ripped of if you habitually over-rev the motor...


Ditto with the AVL head too.


Fit the better valves and springs set offered by our host, as the stock components are decidedly industrial in comparison.

[Leon Novello]

It sounds like this is a brand-new engine you are about to destro- er, modify, don`t forget to wait until it`s out of warranty. Personally, I would have bought a second-hand machine which really working on to play with.

[Waltr]

I work at a dealer as the parts, service and salesman for Moto Guzzi and very soon to be Royal Enfield. The Factory rep gave us a nod to do as we wish within reason. The dealership has a lot of restoration cred restoring Classic European cars that win awards wherever they are shown. That said I do not have any history with Enfield so the input here is welcome.

[jefrs]

Waltr, seriously, I would wait until you thoroughly understand the bikes before waving spanners at them. You need to understand their capabilities and how they ride, and they are fun to ride. But you will need to do a thorough check and service on them before rolling them out the door, check the electrics, check the fluids, tighten and Loctite anything that can rattle off, and make sure buyers understand "running in". Experience on classic british bikes would be ideal but you need you use your demo bikes as test beds to learn their idiosyncrasies; teething problems are often just loose electrical connectors.

You can boost the torque so it's comparable to a V7 quite easily but it's a push-rod 2-valve long stoke with a heavy flywheel, it does not do high revs, so you won't get anywhere near the same horses, not with one 500cc pot. It's not a cruiser (it goes round corners), RE are calling it a "street" bike, it suits a relaxed riding style. Although it is slightly feet-forwards, it suits a slight, forward lean, elbows out, onto the bars, it's comfortable.



It first appeared in 1948 (just six bikes that year?) as the first production bike with a swinging arm, it had some success in ISDT (trials). The indian government placed a big order for them in 1949, these were imports. Madras Motors assembled kit imports during the 50s and full builds from about 1960 (with tooling from England), about which time production of the Bullet ceased in England.

The EFI engine is styled to have the look of the later RE unit motors, it is very different to the original G engines. It is never going to be fast but it does have a lot of lazy torque, that's how you use it and what you might tune it for. You don't rebuild the engine for racing unless you are track racing, even then the long stoke would (piston speed) limit max revs to about 6800rpm, but note the EFI is limited to 5500rpm at the ECU. I linked to my video so you could see the tacho, I was giving it some stick in places (without visiting the scenery) but I was changing up before 5000 because it is running out of steam by then. I did not take it to full chat (old race term for valve bounce, red line max revs) because there is no point doing that.

Jeff.

[Waltr]

I appreciate the input. One of our owners has a 2002 Model 65 so at least I am familiar with the older models but the bikes really do not have the History in the states they do in Great Britain. My whole reason for my original question is doing the 535 kit and valves could be done over the winter to save the summer for riding. I will probably not do much more than exhaust and fuel controller for the demo bikes. Hopefully I will be able to get past the first couple of oil changes before work begins.
It is a pretty exciting time for us, there seems to be a ton of interest in the brand.

[Tim NZ]

>>>I did not take it to full chat (old race term for valve bounce, red line max revs) because there is no point doing that.

[jefrs]

TimNZ, I have taken it to full chat in lower gears and found, no it did not blow up and yes the rev limiter works and protects it nicely. I am given to understand that this engine will run to some 6800rpm without the limiter, which figure is determined by max piston speed. However the engine does run out of urge around 4800-5000rpm so there is little to no point trying to rev it up higher.