Will I get my 100 ready in time for Taupo?

[F5 Dave]

Porosity of the cases is a real concern particularly with 70s Honda casting metal. I believe the terminology of the time described it as "Rice burner Shit metal", but I'm sure Honda had another name for it.


Both cases were bolted together either side to a sturdy custom drilled plate of steel before welding. Makes getting the custom mounting holes in the same place on the next set easier as a by-product.

[crazy man]

its not as silly as a blocked brether in the tank? and then running lean? nice to see it running good.. must have to have a closer look at what you have done

[F5 Dave]

you know the tank 1 way valve did fall off when I dropped the cap, I could have put it around the wrong way, don't think so, but I'll look, but it didn't ever feel like running out of gas.

[richban]

Might be time to invest in some gauges. I am looking at running an EGT CHT gauge to tune the new engine. Especially since I will be messing with ignition soon. Got to be a good option.

[F5 Dave]

I've got a knock gauge but it wasn't powered up / hasn't been calibrated, must do that.

[crazy man]

just run the det counter on my bike.only 1 det after 10mins of running so looking good

[F5 Dave]

Well the fuel cap was on the 50 not the 100.

Another depressing session on the dyno. I've made a number of 'improvements' which 'just have to be better'. Lowering the floors of the transfers so they were flush with the piston crown at bdc, I made a good job of it blended in nicely without trumpet shaping it & also rounding off the bottom of the transfers that I'd never bothered doing on this interim barrel. I'd found the boost port repair I'd done had necked it down so redid it to return close to stock. The head now seals properly.

What I hadn't done positively was seize it, but it cleaned up ok & the ring looks ok, but is it sealing as well? - wish I had a ring seal tester (I'm almost about to make one). Also with the head step gone the compression ratio & squish are a bit low & high respectively. I'd got the barrel skimed but it wasn't enough somehow & squish is 1.2mm & that .4mm extra has lowered the comm over 2 points + I'd reshaped the head a bit as it was a triangular shape.

The upshot of which is on the dyno it was pretty poor but after feeding it some more jets (320MJ up from usual 290) & advancing the ign to max available it almost got back to where it had been, but not as much as on the old f'kd cases.

Another difference from the old cases is the reedblock & reeds. New is a much straighter shot, less obstructed & less necked with a flowed reedblock. Time next to try raise the compression, but also try some new reeds & maybe a dirty unflowed reedblock.

Got home at 10 & decided to make a captive spacer for the front wheel & then another for the spoked hub for the wet wheel. All went well so as therapy I laced the rim & got it to within 5mm of straight & tried it in the forks to see how much it has to come over. 12:30 by then so to bed to be finished later.

[F5 Dave]

Well what I had found was the bore/ring seal was poor. like 36% leakage on a ring seal tester. that isn't good when an aircooled KT100 is ~8-10% for example.

So I'm honed & re-ringed & going to run in on Castor oil.

Engine back together & just needs to get slid into frame for next weekend.

I've redone the head in a closer to toroidal shape & 15:1 comp which is pushing it for an air cooled but should be good for now.

Hopefully this will capture a bit more charge in the head & produce a better power spread.


But will it be ready for Taupo, erm Tokoroa?

[F5 Dave]

Well I can't catch a break it seems.

Over last few meets I've had the RS ign, the RM80 & borrowed RM125 ign all fail. I now have a repaired RM80 one back.

So can I get this to ring seal? I've run a few meetings with castor. ign issues aside I should have a good seal now but my leak tester wasn't playing ball. But I could hear the wind rushing by. It must be leaking still. Last race meet it kind of went ok, but not fantastic. Compared to the 50 its grunty, but not really.

As I lay in bed I remembered how it used to be harder to push start with 14:1 ratio & the YZ piston. Its 15:1 & easy as the 50 & doesn't lock the rear ever if you don't pressure the seat enough like it used to. Waddle forward & dump the clutch. Brrum.

So I lay awake one night thinking about the engine placement & the rubber bushes I borrowed from the RG50 engine to help isolate it. They are pretty sloppy in application, the issue is unlike the RG50 there is no decent front mount. But the whole plot is held in line by the head stay. When you change gear I'm sure you can feel the engine moving a bit as the next gear goes home.

So the headstay is solid (the RG engine has one rear solid & one rear & one front rubber).

Maybe this is twisting the bore enough to cause issues & why I am getting polishing & not enough seal.

So I've made some acetal inserts & the whole plot is much more sturdy, + I'll rubber the head stay so it is never a full issue.

Last race it felt like it was overheating a little & just didn't have enough puff. Ordered a piston at the track for next over time to retry again.

To find when I pulled it down; the ring tips had broken off. Seen this plenty on my old MB50 with 1.5mm rings, but I'm doing pedestrian revs compared to a KT100. Ring ends in open boostport, but plenty of engines like this.


As I said I'm finding it hard to catch a break. By now I'd hoped to have the ignitech & watercooling sorted & be onto the proper barrel & pipe, but I can't get past teething problems. Even so I should be at a decent power level, but its merely ok.

Will it be ready for Tokaroa? Well going I suspect, but I can't see me setting fastest 1st qual this year.

[speedpro]

My ring ends run over the boost port and the motor revs over 14,000. I haven't lost a ring tip. Genuine Yam KT100 parts. Losing the tips will cause big problems. We used to lose a tip now and then on the MB100 sidecar. You knew instantly when it happened.

[husaberg]

Are you using Mb100 cases i guess you are.



Most if not all the H100 have the Front mount, but no doubt you already know this. and are unwilling to give up on your modded cases
I guess Mikes motor is mounted similar using the same bore material and rings, so assuming everything is square and true to the cases some weird stuff is happening for sure.

[speedpro]

Using the front mount is risky. Dipy went through a few cases when they broke. I only use the rear two mounts and have an alloy plate under the head bolts which connects to the chassis rails using little brackets. That alloy plate also provides a convenient mounting place for the radiator and ignition.

[koba]

Most if not all the H100 have the Front mount, but no doubt you already know this.

Ever seen the front 'mount' used to mount the engine?

I believe it's designed for leg shields ad not up to the task, so I've been told.

[husaberg]

I just read Mikes post i wasn't suggest to ditch the top but if Dave is right with his theory and he uses the other three mounts as well.
I guess Mr Dipose might have not used all the other three and- or deleted the balance shaft.

Ever seen the front 'mount' used to mount the engine?

I believe it's designed for leg shields ad not up to the task, so I've been told.

like the CR80

http://www.cyclechaos.com/images/thu...Red-8411-3.jpg
If you don't believe me have a look at the crankcase of a 80-83 model and see the unused half machined balance shaft housing.

The cylinder spacing of the 100's the stroke of 50 but with a bigger pin. The air cooled CR80 is a mix and match of the H100 and MB100 and MB50.
H100 Cr80
But yes some of the last H100 had a fo-full cradle but it was a bolt up section. doubt it did much other than making it look more acceptable.

The later MBX and so forth had conventional frame and very similar crankcases as well.
Later the mounts although very similar are actually different position to the Cr80?mmmmmmmm not so sure now..........

[F5 Dave]

My first iteration used the front mount, this was 15 years ago & shortly after when others were starting to mount MBs into different frames they were breaking cases. Those front mounts are on a really thin part of the cases. Dave was by far not the only person to find this, I've replaced cases for John's bike & there was another set in his collection (bought from someone else) thus afflicted. H100s are the same, well almost the same, but for point of this conversation the same.

CR80 has much more webbing.

So next iteration was not to have that mount used.


I had to cut the std top mount away as the big carb would have hit it. That sounds silly but case reed is very different from Mike's picture, although there is Frits's idea of shortening the inlet that could sidestep that but create other case problems.

Either way if I had a custom set of mounts for the top I might as well for the bottom as they stick a mile away from anywhere useful on an RS chassis. Besides the cases were custom to make them case reed. I have a plate for making new cases in the same place.