Siebenrock 860 kit running hot

[donbmw]

Yes it’s the upper cross over bar. I installed oil pan spacer on my 75 R90/6. Removed and installed the cross over bar just below the pan.

[mpe]

 Is this kit engineered to function correctly with stock carb jets and settings? It seems to me that increasing displacement by 1/3 is going to require more fuel, maybe move the needle up as suggested, maybe even larger jets. Or put big Mikunis on it. LOL

[dogshome]

Is this kit engineered to function correctly with stock carb jets and settings? It seems to me that increasing displacement by 1/3 is going to require more fuel, maybe move the needle up as suggested, maybe even larger jets. Or put big Mikunis on it. LOL

If you keep the stock air filter and exhausts, yes. I have keihin stainless OE copies and stock airbox. Open exhaust, K&N, big valves or cam change etc would require re jetting.

I don't purport to be a jetting guru, but this kit is a midrange improver. No rpm increase, so no gross change in flow. Just happens at lower rpm.

Big mikunis probably not going to do a lot as the 650 valves, ports and small combustion chamber diameter remain. The 450 to 860 conversion even less-so. 

I'd start with a 1000 and work from there if spending that kind of £££ 

[mpe]

What color are the spark plugs?

[Tony Smith]

High temps are a new one on me. I live in North Queensland, Australia where 30 degree (Celcius) give rise to conversations about how nice the cooler weather is.

After I fitted the 860 kit I pulled the dipstick temp gauge off the shelf where I put it years ago because it said things I didn't like on my 1978 RS.

Anyway I see temps in the 120-130 degree range as a matter of course. Deep sump, no cooler.

I stuck it onto the wife's R80 and it said dcthe same thing.

I am unconcerned

[Kelvin]

Hi all,

Many thanks for the comments and suggestions.

I've now done 4,000km since installing the kit. Particularly, I'm just back from a 5 day sojurn in the Australian Alps, southern New South Wales/northern Victoria.

I've not again seen 140 degrees so I'm putting that down to the initial bedding-in period with the new pistons and barrels. It fairly often gets up to 130 degrees, and a bit more, but I was doing some spirited riding and returned home in 38 degree heat, so this isn't a concern.

With regards to the other suggestions: the plugs were a normal colour, nothing to suggest rich or lean. The spark was advanced, but not so much as to cause a change in temperature. I've found it runs nicely on 98 octane and haven't tried 95 or ethanol (locally the 10% ethanol fuel is typically 94 or 95 octane, the premium 98 is not diluted).

I'm not at this stage considering a deep sump or an oil cooler.

As dogshome suggests the kit improves midrange, I'm really enjoying the ease of overtaking and the reduced number of gear changes. However, it lacks something in the top end, over 6,000 revs and open throttle (the LS redlines at 7,500 revs and I routinely  run it between 5,000 and 7,000). So, I'm going to  increase the main jet size but not alter the needle clip position: the mid range that the needle jet manages is already sweet.

Cheers,

Kelvin

[dogshome]

Thanks for the feedback 

Don't expect too much at the top end. It only has 650 breathing and a very dodgy squish arrangement.

P.S. It's a balmy 4C here right now. I had to take my jumper off! 

[Kelvin]

I've done another 2,000 km on the bike but with 145 main jets. These are three sizes up from the original according to Motobins website (138 -> 140 -> 142). The bike now pulls strongly at high revs. Disconcertingly it has always "run out of puff" above 7,000rpm, which has made it easy to avoid redlining it. It is now still pulling as it accelerates upwards of 7,000, which makes me a bit concerned that I will redline it (7,500).

I haven'd calculated fuel efficiency but it hasn't completely killed its range (I got above 330km without going onto reserve). I've used both 95 and 98 octane fuel.

The temperature got regularly to 130 celsius but only up to 140 riding in 36 degree heat (97 fahrenheit). So, I'm no longer concerned about the temperature implications of the Siebenrock kit.

[dogshome]

Thanks for feeding back again, threads left open are always frustrating when you are searching to fix a problem 

Interestingly, the main jets in mine are 145 as stock. I checked against this chart when I did the upgrade, with the carb numbers.

https://bingcarburetor.com/uploads/9/8/7/9/98794296/bmw_jetting_chart_cv_carbs.pdf


I wonder if that is an LS thing (exhausts?) or a country / emissions difference? It might be what day of the week they set that model up, or an early dieselgate for magazine road testers 

[georgesgiralt]

Hello,
I was fortunate, in the early 80s to get a factory manual for the R65. It came with a set of updates. And showed that every year they changed either all the jetting or the needles position.
And, when I put her back on the road, I tuned her up because the fuels of today have changed a lot since the eighties.
In my case, the main jet was too big but the needle was too low.
I used this procedure : http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune%2CCV%2Chigh_rpm_engines.html it is easy and fast. But you have to have a set of jets to perform the operation. Not that expensive, but...
I can give the BMW P/N if you need.