#6

[koba]

On a completely different tack, I have been messing with Gary's MB100 engine. Finally put it on the dyno after work with nice improvements from the test done earlier. I had to up the jets a couple of sizes and backed the timing off a bit. The power is modest but it'll be easy to use. The needle may have to go down one notch but we'll check that on the track.

What would you put the power range at in revs?

[speedpro]

8-11K at a guess. It seems low revving and flat. Peak is a whisker under 20rwhp so lots less than expected. There's a couple of things I didn't check before assembly and the pipe though good, had a similar effect on the motor previously where it seemed flat. We'll run it on the dyno and try a few pipes I have lying around including a copy of my 30hp pipe. Wobbly has a new pipe designed specifically for this motor setup so will have to ask nicely for him to send it.

[speedpro]

Also . . . I managed a few laps on the FZR 125/2 today. It actually wasn't too bad. As I knew from dyno runs it won't rev out as the small injectors just don't have time to inject the fuel over 15K rpm. Plus it's way overgeared and I only used 1st & 2nd. If I could run it out to 18K I'd only need 1st. I had the turbo inlet plenum manifold fitted to reduce the risk of something going down the intake and it didn't seem to adversely effect it on the dyno and no problems on the track. The throttle is a pain needing over 1/2 turn for full throttle. The engine is pretty weak but runs sweet with only a little burble here and there. On and off the throttle it behaved very well with no stuttering or hesitating. I'm very happy with how it ran and am even more convinced now that fuel injection is the way ahead.

[koba]

8-11K at a guess. It seems low revving and flat. Peak is a whisker under 20rwhp so lots less than expected. There's a couple of things I didn't check before assembly and the pipe though good, had a similar effect on the motor previously where it seemed flat. We'll run it on the dyno and try a few pipes I have lying around including a copy of my 30hp pipe. Wobbly has a new pipe designed specifically for this motor setup so will have to ask nicely for him to send it.

Would be good to get an extra thousand over-rev...

I'm now convinced that power/power-range balance is far more important than the total horsepower number, for kart tracks at least.

[goose8]

. . .time to give it a big blow out tonight and go for some wins

Fixed it for you.

Yeah that's my usual training too. Less on the vodka these days. More a nice bottle of wine. Or so.[/QUOTE]

Well the ten beers last night might of been just what I needed got seven wins an a second bike was great all day .

[koba]

Fixed it for you.

Yeah that's my usual training too. Less on the vodka these days. More a nice bottle of wine. Or so.

Well the ten beers last night might of been just what I needed got seven wins an a second bike was great all day .[/QUOTE]

Hmm, that's a good idea, taking it easy and only hitting ten beers the night before a race day.

[speedpro]

Tried Gary's other pipe on the bike tonight. A quick measure showed it was short by 30-50mm so I wasn't expecting much. The graph compares the best of the runs made with the pipe I made for a different specification motor. That pipe is 30mm too long but worked OK even if the power is down. The short pipe evidently has small sections missing, 1 or 2, which were left out by the person who welded it together.
You can see the graph has a surge after peak which will be the pipe. I had to jet it down 2 sizes and advance the ignition about 5deg to get this curve. It clearly was never going to match the first curve. It is a very good example of mismatched tuning of parts.

[speedpro]

I hate that

[speedpro]

More stuff to hate. Has to be the worst I've managed so far. It even leaked gearbox oil.

[Skunk]

Looks like your avatar. What, where, when.


If it ain't smokin' - it's broken.

[cotswold]

Is there anything left to salvage, can't remember seeing such wholesale carnage before.

(hope you don't mind but I've shared a couple of your pics on a different forum, they are so horrid they need a wider audience )

[speedpro]

Looks like your avatar. What, where, when.


If it ain't smokin' - it's broken.

Max revs on the dyno, top gear, just shut it off. It made a funny noise and I grabbed for the clutch but it went "clack" before I got my hand to it. Something had gone off since before the last meeting and it was a couple of horse down. I had tried a few things inbetween times and was just checking settings to see if it was that. Evidently not. Spread the collection of MB and H bottom ends out in the garage, decided which cylinder we'll use and should have the new motor together tonight, or I might get in and do some mods first. Pretty sure which mod caused this so won't be trying that again.

[F5 Dave]

That plug will never be the same again. Cheap insurance, I'd suggest replacing that.

[speedpro]

New plug(just for Dave) new bottom end, old H100 cylinder, old pipe. Making essentially the same power as before but not as nice and wide. We tried the good pipe hanging out the side and the broad power came back but with a dip between two peaks. The dip is about 1.5hp and the peaks are similar values. It isn't a surprise as this cylinder is different to the MB that the pipe was built for. I widened the ex port 2mm each side and raised it about 2.5mm. The transfers have the specified timing but the T/A has to be way down as they are otherwise stock. The angles are all wrong as well but I'll devcon them next week to sort that out. I was going for blowdown T/A with the ex port being 70% of bore diameter, across the chord. All the increase in ex port size is above the transfer port top edge height. The ex port duct has been left at the original small size. The port itself has been enlarged but tapers down over about 15mm to the original size duct. The outlet of the duct is too large so without machining and installing an insert it was the only option for a reduced ex duct. I need to talk to Wobbly to see if cutting steps in the alloy inside the duct will work, instead of having a small duct extending right out to the pipe, with the flat top and bottom of the duct forming steps into the round pipe. It looks OK on the dyno especially with the good pipe but is peaky with the old one. Just need to fill Gaz with coffee and sugar and we should be good.

Cricket will have to put a bit more effort into getting the right gears out of corners though he is getting pretty good at hammering the clutch.

[speedpro]

Well I finally brought myself to butcher the best pipe I've ever made. Now it fits the H100. Gary owes me for emotional stress big time. Before and after pics below. I had to justify it by considering what could be done prior to the GP for best effect and the pipe wins by a mile. A couple of runs on the dyno on Friday to confirm jetting and it'll be all good.