first ride today

[chrisshrops]

Well at long last I have finally made my box of oily old shite into a working r100 naked bike ,got it an mot and taxed today so I went off for a shake down run
The bike starts first time and ticks over nicely it picks up ok however there seems too be a huge flat spot around 3000,rpm once it hits 4000 it goes better ,not the result I was hoping for
its running on a Keihan exhaust stock jetting with a moore speed pistons valves and gas flowed heads.
I reset the carbs and checked the timing was advancing but its no better any ideas chaps ?
other than that, man do I need a new rear shock ! and better damping up front the twin four pot brakes make the front end dive like a sperm whale lol

 

[solidstate100]

With the engine mods, my guess would be re-jetting is required. Have you checked diaphragms in carbs are in good condition and working correctly? cables synchronised etc?

 

[chrisshrops]

I will put a bigger main jet in next week ,the carbs had a total strip and rebuild ,I think the main jet is a bit on the small side
Thanks for your input ,I'm going too order a hyperpro rear shock and front springs too see if it sorts the harsh ride out

 

[Rambozo]

I fitted richies high comp Pistons to a friends r100cs a couple of weeks ago and it's
running great with no carb changes and a stock keihan system

Maybe the gas flowed heads make a difference? Jets aren't dear so worth experimenting, maybe try needle height too since that's free

 

[Rob Farmer]

Main jet isn't the issue at 3-4k and if it was your more likely to need a slightly smaller main jet.

As rambozo says I'd be looking at your needle position first. Your best bet would be a dyno run and ask for an air/fuel plot against rpm, this saves the guess work.

my moorespeed engine has gas flowed heads and it needed a smaller main jet.

When you say keihin do you mean it as a keihin y piece? If you do there's a good chance that this is your problem. The keihin y piece is the work of the devil and screws up the midrange completely. You really need a balance pipe if it's a GS.

Just out of interest what bike is it?

 

[chrisshrops]

Thanks chaps ,it's an rt based bike Rob ,I have it on a standard road keihin system with the h set up
I'm on the 3rd notch of the needles I have a selection of jets on order and see how we go
I will have a check and see who does dyno work in the west minds

 

[Beemerboff]

Not everyone gets the same result with the Kenihan h piece, mine works fine, probably better than stock. But my can flows flows a little more freely than stock, and I have a balance pipe at the front, no snorkels in the air box and the needles in the second groove from the top.
My Boyer ignitions all work perfectly too.
Well set up forks will dive under brakes- if they dont they are wrong, and the easiest way to counter dive is to add a little more fork oil - air is actually progressive, unlike a steel spring which is not.
Only tried Hyperpro springs once, on a VFR, and they were the completely wrong springs for the bike, about two or three grades too still , so knock about 60 KG off you weight when you order them and you might get close.
Racetech have a good website, their springs are a good bit cheaper than Hyperpro's and work well for me at the correct weight,

 

[Rob Farmer]

I assumed it was a Gs based bike.

A dyno run should cost around £30. It takes all the guess work out of things, saves hours of tinkering and unnessasery parts.

I suspected your running way to rich on the midrange which will need your needle dropping instead of lifting. That flat spot is more than likely your poor bike clawing it's way out of a huge over rich mixture. If there was no sign of pinking then it's worth dropping the needle until it does and then go back a notch.

If you have the snorkel air box fitted you could swap it for either an earlier RS clamshell or a moorespeed filter.

One of the problems with the bings is the lack of main jets available. I went for dellortos on my moorespeed engine but with hindsight or if doing it again Id go for mk11 amals. Lovely carbs with a huge selection of jets and needles.

 

[chrisshrops]

Thanks Rob
Thats great I will drop the needles a notch and see what that does ,and will look into the clam shell or one of Richies k and n filters and see how that works
I forgot too say mine was a 94 bike that had the stupid clean air kit fitted, its not on the bike now and all the boles for the pipework have been plugged

 

[chrisshrops]

Have had a chat with the ever helpful Richard, I have a few things too check in the carbs as he says it should run well from stock settings

 

[chrisshrops]

Any of you guys had any issues with thick carb diaphragms ? I had the carbs cleaned and rebuilt and I don't think the diaphragms are BMW , I stripped and checked over the carbs today and everything else was spot on

 

[Rob Farmer]

The diaphragms made for the stromberg carbs fit. These are a fraction of the price of BMW ones but don't resist modern fuels well. Can't say I've had any issues with them.

Get the dyno run in and the issues will be obvious. You'll be messing around for months otherwise.

 

[chrisshrops]

I'm looking for a dyno shop at the mo Rob l will have a phone about tomorrow .

 

[Beemerboff]

Rob, always wondered why you didnt try the Amals - I am using the MK 11 inlets rubbers with my Bings and they fit perfectly so no problem there, and most of the problems like soft slides and float levels have been addressed buy Burlene.
But stick with Burlene for parts if you do - I bought needles from a BSA specialist and they were just plain ground wrong, took months of farting around until I worked out what the problem was.

 

[chrisshrops]

Thanks for your feedback chaps ,ots all helpful as this is my first bmw airhead
Im not that clued up on it

 

[Rob Farmer]

Rob, always wondered why you didnt try the Amals - I am using the MK 11 inlets rubbers with my Bings and they fit perfectly so no problem there, and most of the problems like soft slides and float levels have been addressed buy Burlene.
But stick with Burlene for parts if you do - I bought needles from a BSA specialist and they were just plain ground wrong, took months of farting around until I worked out what the problem was.

I went for the dells because it was easier to get mounting parts, however I've been plagued with floats that keep sinking (four so far) I've taken them off now to run bings for the short term. Wish I'd gone for Amals from the start.

 

[chrisshrops]

Following some sage like advice from Arkwright I put a 150 , main jet in and set the needle third slot from the top and it flys along
I will book some dyno time when the top end is run in and see if I can get it better .
The front forks will get a touch More oil and some new springs from race tech
Thanks for your help so far folks , I will post some images soon

 

[chrisshrops]

I forgot to mention I am running continue classic attack radials on the rt ,and it's fair too say they are ace ,much much better than the avons I had on my last classic bike

 

[Rob Farmer]

150 seems way to small. I tried them in mine and had problems at the top end, still they're all different and you really need the dyno printout.

 

[chrisshrops]

Yep it had a 135 as standard Rob they are 32 mm carbs ,once I have a few more miles on the bike I will get it on the dyno and see were it needs adjusting