1979 R45 - 860cc Siebenrock upgrade kit. Any experiences ?

[tedmagnum]

For those who are interested.

Fitting the Siebenrock totally cured the problem with the racing engine.  I can't say exactly how or why. But it did.

For those fitting an 860cc to an R45,  the kit fits perfectly and works well.   I had to contact Siebenrock for confirmation. Such as whether to fit the large o-ring to the base of the cylinder (In my case not as it's early 1980 model). The bike does rev up EXTREMELY quickly though. In a good way. I think a longer ratio bevel box may be beneficial in the long term though.

I up jetted one size and it seems to be correct.

I sold the bike a few days later. A friend tore my arm off once he saw the engine work.

All in all, I was extremely impressed with the quality of the kit. Excellent and accurately engineered. I wouldn't hesitate fitting another.

[dogshome]

Nice one. Glad its fixed and thanks for reporting back 

I'm just about to fit an R80 final drive to my 860. The ratio is not much different from early 650 to early 800, the 31/9 to 37/11 is only what the later 650 had anyway. I can imagine 35/9 or 38/8 that the 450 comes-with DOES rev up fast with 860 kit.

[Adrian]

Hi there - I have the 860 kit fitted to my rebuilt R65.
.
Without any real detail - I'm a bit long winded usually - I am very pleased with the result. More power for two up riding & my favourite place the Adelaide Hills.
.
It will transform the bike 👍😊

[stubmw]

For those who are interested.

Fitting the Siebenrock totally cured the problem with the racing engine.  I can't say exactly how or why. But it did.

For those fitting an 860cc to an R45,  the kit fits perfectly and works well.   I had to contact Siebenrock for confirmation. Such as whether to fit the large o-ring to the base of the cylinder (In my case not as it's early 1980 model). The bike does rev up EXTREMELY quickly though. In a good way. I think a longer ratio bevel box may be beneficial in the long term though.

I up jetted one size and it seems to be correct.

I sold the bike a few days later. A friend tore my arm off once he saw the engine work.

All in all, I was extremely impressed with the quality of the kit. Excellent and accurately engineered. I wouldn't hesitate fitting another.

Hi tedmagnum, did you , or anyone else for that matter fit the asymmetrical camshaft from Siebenrock when fitting this kit? They seem to recomend it for the 27hp R45. I'm assuming mine is the 27hp as it has the 26mm carbs .
 From what i can see around the net it may be a major engine strip on the pre'80 models, '78 in fact, to install the camshaft on these, am i right? Or is it relatively hassle free (hoping!)? I think i have a link in the timming chain, which could help!

[Tony Smith]

Changing a cam is not difficult if you are careful and clever
I am not clever, but the person whose taught me this trick was definitely clever.

Remove rocker cover and loosen all tappets, remove be the pushrods you can, then turn engine cover ver la me turn and remember be the rest.  All of the can followers are now as far up their bores as the cam can push them.

An essential "special tool" at this point is a thin piece of dowel with a small and strong rare earth magnet glued to the end.

Next remove timing cover, beancan, alternator rotor and stator and diode board.

Next timing inner cover.

Set the engine to TDC and then remove timing chain.

I cannot recall if the n the R65 you can get at the front camshaft bearing bolt without taking the sprocket off. Either way once the bearing retaining bolt are out carefully withdraw the camshaft forwards

If any cam followers have sneakily slid down their bore, now is the time to use the dowel and magnet to draw them up.

Do not move the crank and when the cam comes out note the orientation of the front me at lobes and the flat tang that drives the oil pump.

Assembly with a new cam is the reverse of the process to remove the old one.


Please, please, please. Unless you are moderately comfortable with doing on engines do not attempt this as whilst it is moderately safe, you can fsk the engine majorly if you get it wrong.

I have never done this on a R65 but many years ago I changed the camshaft multiple times over a couple of days using a dyno to test the maker's claims. The best one was a sport cam made by Australian guru Don Wilson, the person who taught me how to change came with bulk stripping the engine.

Funnily enough my R65 wears a cam made by Don but never put to manufacture as he felt the target purchasers of R65s wouldn't be interested

Gee I miss him.

[dogshome]

I have to ask that if you have the small valve R45 heads, will a cam swap make any difference? The 400cc boost obviously does, but tuning the cam profile to something with very limited breathing seems illogical Captain!

It's an expensive mod for probably very little return. Tuning for RPMs or flow with a massively overbored engine does not make sense. Unless you want to sell engine parts........

[georgesgiralt]

But the OEM camshaft is unobtainium now. So the Siebenrock "power" camshaft is the only option if your camshaft is toast....

[Tony Smith]

I have to ask that if you have the small valve R45 heads, will a cam swap make any difference?

I am inclined to agree. My feeling is that spending the large wedge of cash on the 860 kit should be accompanied by fitting the best heads you can justify. In the case of the R45 that means late R65 heads. Anything else is going to require a new exhaust system.

I still kick myself for not fitting big valve R100 heads.  Ah well!