Bimota Forum

[tenchu2x]

Thx for all your feedback!

Yes I have 102 fuel in it.
I also thought of trying carb cleaner additive before pulling the carbs out and cleaning them which is a lot of work.

I ordered this :[url]LIQUI MOLY 5100 mtx Vergaser Reiniger, 300 ml https://www.amazon.de/dp/B001NFIQBG/ref=cm_sw_r_cp_api_i_-w7rDb48N5B86[/url]

Any experience with it ? Let’s see if it works...

[2bims]

I think the German language...or rather most folks on heres ability to read it is going to reduce your chances of a response...but...It does have a lot of reviews on the product and 4.5 stars out of 5 is not to be mocked....fingers crossed for you

[tenchu2x]

well yes its a carb cleaner that SHOULD work by just putting it in the fuel.

i mean it is worth a try. i guess if the jets are really heavy blocked it wont work but for the money its worth a try.

i mean i do know in general how to open a carb and clean it with ultrasound, i do this with my older bikes. but they have Dellorto carbs that are removed within 1 minute and only 1 or 2 cylinders´, so only 1 or 2 carbs.

4 mikuni carbs is a lot more work and also i guess removing them is not a breeze...

[YBista]

If the LiquiMoly fails to work it would also be worth trying the RED LINE Si-1 fuel system cleaner at about £15 for a 15oz bottle.This stuff is VERY good.Best approach is to add the whole bottle to about 1 gallon of fuel and just RUN the bike for a couple of miles each day , for a week or more. That way you maximise the time exposure of the cleaner to the undoubted gum on the pilot jets .If that still fails then (sadly) you will nèed to strip the carbs.
GOOD LUCK !

[tenchu2x]

Great tip!

Are you sure the whole bottle for just 4 Litres of fuel ? Isn’t that too much?

[YBista]

I know it sounds excessive ,but I have done this many times ,so use the whole bottle in c.1 gallon of fuel and let time do it's thing. If you personally feel it's too much ,then 50% of the bottle would be an acceptable alternative ,but the key thing is the repeated short term running over multiple days to maximise exposure ,as the fuel will evaporate in the carbs bowls relatively swiftly ,nullifying the benefit of the cleaner (not in contact with the pilot jets..).
It is highly likely that only a couple of the pilot jets are badly gummed up ,caused by the bike being left on the side stand which causes the fuel to empty from the float bowls at different rates . Obviously this is irrelevant to you unless you need to resort to a carb removal and strip down to ultimately fix the problem (If the cleaner approach fails).if you are forced into this position don't worry as it is not too onerous ,but there are some tips to make the process easier .suggest you focus on the cleaner option 1st.
As regards prevention of reoccurrence the advice is simple:
1.don't let old fuel stay for long in the bike ,ie ride it more!
2.use low ethanol fuel,e.g. super unleaded and definitely NOT e10.
3.when laying the bike up for more than 3 months use a fuel stabiliser.Plenty available on line or at any lawnmower shop.
Finally, just to assure you that this problem is common on the BIG YB range ,especially with increasing ethanol content of fuel, so don't think it's just you !!
GOOD LUCK.

[tenchu2x]

The liqui moly did not really help... let’s try the other now ...

I was wondering why no one mentioned the spark plugs... is there a reason for this ?

[rOLLI]

Recently my YB8 wont start because of problems with the high voltage wires of the spark plugs.
The reason was, that I moved the motor down for some reason. In this case I forgot to disconnect the spark plugs, so the high voltage wires got too tighten. I didn't recognize this. But afterwards, some sparks didn't work. I moved the wires out of the the ignition coils and fit them new. The problem was solved.
Only throwing the wires back into the ignition coils could help.

The high voltage could be testet with a stroboscope lamp..... roland

[tenchu2x]

I noticed that it is better as long as the machine is still cold and gets worse when the bike gets warmer.

Is that logical ? I am not sure

[Jonny B Bad]

It's too rich at the bottom end, because the float heights are not set high enough. Get in there and measure where the floats are now - anything below 12mm and you know you've found your problem. Replace the float valves (and the pilots, if it's sat for a while) so you've got a reliable base to work from and then set the float heights to 15mm (I know the book says 12-14mm, but that's not enough). While you're in there check:

Mixture screws - how many turns out? O rings should be replaced
Needles - which notch are the clips on & what else is on the needle - spacer, washer?
What size mains are in there?
What size pilots are in there?
_________________
What, Jonny's gone!

[tenchu2x]

ok, i notived that at least one of the carbs is leaking from the Reservoir. so any way i Need to take them off.

Problem is : i dont have a clue how to get them out? i mean it is not possible to access anything due to the Frame structure.

i did a Picture, can you guy tell me how i should start to remove those? i am really stuck here...

https://imgur.com/gallery/04BzaFL

Cheers Robert

[Bud977]

You will need to make a tool to get to the manifold rubber clamps.

The one I use consists of a 1/4" drive handle, then a universal joint, then a short extension, then the torx bit. Have a look down the front of the carbs and you will see the clamps and screws.

[tenchu2x]

@bud: sent you a pn

Cheers Robert

[YBista]

Hi Robert,

Here are a few tips and comments on how to tackle the carb removal,following 20 years of playing with the Big YB models...Hoping some of them make sense and are useful:
1.remove the fairing ,makes everything easier.
2.make sure the engine is warm before you start removing the carbs,to ensure rubbers are warmed nicely.
3.the 1st removal will be the difficult one.All subsequent ones will be much easier.
4.take the opportunity to do all "fairing-off" jobs whilst you are doing the carb removal (oil/filter change,exup clean/lube/adjust etc )
5.replace the carb/engine inlet rubbers with Tourmax version. Yours are c.30 years old and the Tourmax version is good,soft and cheap (c.£30).This will help all future remocals/replacements.
6.replace all cross head carb screws for the tops and float bowls with stainless steel cap screws whilst you down this far.
7.For reassembly position the engine side clamp for the carb/engine inlet rubbers with the screws positioned at the front of the rubber.The carb side clamp screws should be placed at the rear of the rubbers.All screws should be aligned across the frame ,ie pointing at 90 degrees to the direction of bike travel.All screw heads should be facing into the centre of the bike , ie so that access is always from the other side of the bike that you are working on.
8.Once reassembled all future removals should be actioned by undoing only the carb side clamp,ie do not touch the engine side clamp .
9.Use WD40 on the inlet rubbers to aid refitting the carbs.
10.clean and grease the choke lever whilst the carbs are off, as you need to remove the choke cable from the carbs .
11.The idle speed adjuster bracket should be removed from the cross bar .I do not re-bolt it to the cross bar on reassembly, but merely leave it "loose" below the carbs , but correctly pointing to the left and attached with a zip tie to stop it flapping about.
12.loosen the throttle cables at all adjusters and (ultimately) when the carbs are lifted away from the engine)remove the cables at the carb end . Reassembly is best done with a pair of forcep pliers (medical tool etc ).
13. Choke cable is best removed (at the carb end)and reassembled in the same manner , ie when he carbs are pulled away from the engine by a couple of inches.
14. In addition to a pair of forceps there are 2 further tools that make this job a breeze . I think you are in Germany but I am sure you can get there:
A)Snap On 3mm ball end long 1/4inch socket (code TMABM3E)
B)US-PRO 600mm long flexi 1/4 inch drive screwdriver .comes as part of a set of 3 , but all are excellent tools.Not sure of the part number but check out AB TOOLS in the UK .their product code is AU 042.
Both tools are about £19 but you will NOT regret the expense.

Just let me know if any of this is unclear . Best of luck.

[tenchu2x]

thx for your massive support!

i am getting there. carbs are off already still need to fit them back in. some questions still: