HO cam

[chanito]

:'(So, i put together a big bore engine for justintime, and it soon was overheating, he changed the head gasket and still was overheating, and i ask to have the engine back to take a good look at it. Once i got it here i took it apart and inspect it, i discovered that the timing chain upper guide was broken and some parts has scratched the water pump housing, there was no water leak yet but the wall of the pump was damaged and the head gasket was not leaking, so i had to check further, i discovered by checking the head that the combustion chamber was smaller than usual, so the compression ratio was to hi for pump gasoline, so i had to unshroud the valves to raise the combustion chamber volume and decrease the compression ratio.
To avoid further problems, i installed the engine in Katrina, but like an idiot i had the impact gun set to tighten wheel nuts on cars and broke the long bolt that is the pivot point of the swing arm, luckily he had an extra one and send it to me, i installed it by hand and road tested the engine, so far so good, but since i do not have the HO cam and his engine does, i discovered some funny stuff regarding the HO cam, the cam is way big and the idle is kind of loopy specially with a light weight flywheel, also the power band is shifted up on the revs so instead of having the torque peak at 6k it is closer to 7200 rpms, so you need to install lighter rollers (weights) on the variator, and probably a bigger slow jet might be a good idea on the stock carburetor, so the engine becomes kind of a sleeper until it comes on the cam sweet spot and them it pull like a turbo engine scaring me a couple of times, because i ride in the city and the engine reaches the sweet spot when i am less than a block away from a street light, the scooter takes off like a banshee and i have to slam on the brakes to get the scooter to stop, it must be super nice to ride in a place with long straights with a light to see what it can really do.
So installing a HO cam will involve getting intimate with the variator and the carb to get its potential
Sadly i have to return the engine, but since i have to rebuild Katrina engine anyway (crank bearings) i am planning on installing the cam from 970 performance and see what it can do with some tunning

[jedisabre7]

good info, thanks for sharing chanito.

[thunderstRuck]

Now if someone could come up with stiffer valve springs I wouldn't get that crazy rattle @ 10,500 rpm.

[justintime]

I didn't think there was a HO cam installed on that motor. I received it from sanjuro. As far as I know, it was stock when I sent it to you. I'll send him a PM on TR to see if it did, but I wasn't aware of it. Where'd the HO cam come from?

[justintime]

Sanjuro was unaware of a HO cam being installed. I think the ruckus he bought was for a motor swap, and I got the original. I didn't notice when I replaced the head gasket the first time, as I've never torn down a motor other than the one you have. So I wouldn't have noticed a difference between the HO cam and the OEM one. ;D Must have been a freebe ;D

[chanito]

maybe is just my jetting
anyway your engine is Ok now, i still have to go to the bridge again, probably Wednesday. I had to install some spacers between the radiator cover and the radiator as the top of the cover touched the top tub, acting as a heat sink on long straights

[delslo]

Have you ever thought about removing the "fan" and installing a electric one? old cars benefited from removal of the fan clutch and go with electric...

[thunderstRuck]

Oct 6, 2008 17:44:00 GMT -5 justintime said:

Sanjuro was unaware of a HO cam being installed. I think the ruckus he bought was for a motor swap, and I got the original. I didn't notice when I replaced the head gasket the first time, as I've never torn down a motor other than the one you have. So I wouldn't have noticed a difference between the HO cam and the OEM one. ;D Must have been a freebe ;D

There is no difference to the naked eye. I measured the lobes and wrote down the diference between stock and HO, it was negligable.

[delslo]

What about the electric fan idea?

[smartbomb]

Does anyone know the differences between the stock cam, the BSS cam and the 970 cam? I have access to a cam doctor and was going to measure the Stock vs BSS cam but if someone has the specs, it would save me time and work.

I have a stock and a BSS cam. Does anyone have a 970 cam that I can measure?

Chanito, I can't see how lacking power below 6k is that bad, heck my motor is never below that. My clutch enagues around there and my rpm jumps to 8K almost immediatly due to my clutch and variator tuning.

I don't think too many Ruck riders spend much time below 7200 rpm.

[thunderstRuck]

Measurements: (mm)
Stock: IN: 29.20
Ex: 29.26
BSS(970) IN: 29.40
EX: 29.59
These were measured with a digital micrometer. That's the official numbers, do with them what you will.

[chanito]

It was a dirty carburator, as i had bad crank bearings so i have been runing the wife metro, then i installed this engine and got this performance and i blamed it on a non existing HO cam
I need to have mid range pull as i ride on the city with a lot of stop and go and slow traffic

[seansean]

So what you are saying is the HO cam might not be too big? From what I understand talking to all the different cam sources over the last year or so, they all have come up with basically the same cam. But measurements on all would be nice.

[Dandy Dan]

I've used the Battlescooter HO cam with fairly mild but postive results.

[seansean]

Does anybody know what the manual means by P-type cam ? In my Met manual, it has two options for the cam. In section 8-9 of my 02-06 Met manual it says that the service limits for the cam are
IN. 29.2065mm EX. 29.2067mm but then under that it says
[P-type] IN. 27.8623 EX. 27.9217

What is that all about, and why are they so different?

[chanito]

The metropolitan had a restricted vertion, called the metro II, so they used a milder camshaft on it

[seansean]

Wow. That was too easy then. I hadn't realized that the went as far as having a different cam for the Met II. I figured they just put a restrictor plate in the intake manifold and maybe one in the exhaust. It's crazy that there is such a difference in the two Met cam sizes compared to how little there is between the normal cam and the HO cam.

[Dandy Dan]

yeah they really went the extra mile to restrict the Met 2, there was the cam, restrictor plate, carb diagram spring, ECM, variator etc.

[smartbomb]

I think someone should make a bigger cam for the GET. If you got your clutch adjusted right, you never see the lower rpm anyway. My built engine with a BSS cam has way more bottom end than stock, in fact most of the big power improvments are in the bottom end.

[chanito]

I would love for some one to get a nice small engine dyno and do some testing on a ignition map and camshaft profiles