Rev 3 270 - Fueling And Ignition Timing

[theflyingferret]

Hello all,

I'm looking for some general engine setup advise on my newly acquired 2000 Rev 3 270.

It runs well enough most of the time but does have a few issues:

1) Pinking - It's only minor but consistent when you get off the throttle the low to mid RPM range...especially if you've been running under load at higher RPMs like up hills between sections.

- It might be the *****, low octane petrol we have here in the States. I'm using the highest octane stuff I can get at the pump but I refuse to pay triple for race octane stuff.

- Thought also it might be running lean so I've lifted the needle in the Carb one groove down on the circlip which has improved it slightly.

2) Starting - Sometimes it's a one kick bike, the rest of the time you have to remove the plug, dry it off and then drip a few drops of petrol from your gerry can nozzle directly into the cylinder before putting the plug back in...it then fires up first kick.

- This one's got me stumped...it's more problematic after being on the trailer than right out of the shed so I'm going to try corking the silencer when in transit.

- Plug is the right one and it's brand new.

3) Stalling down hill - it does this on longer, steep downhill sections...it's either getting slightly flooded or leaning out.

- Mikuni Carb I hear you scream!!! Nope, I'm running a 1yr old (according to the previous owner) Dellorto VHST26.

- The Dellorto doesn't leak a drop, I've turned the idle screw in 1/4 turn and it's idling a little faster than I like it but helps with the downhill problem.

So I think a lot of this can be sorted by setting up the Carb properly and possibly adjusting the Ignition Timing. I've had the Flywheel off to clean out the casing and the coils after riding through some deep streams (Why don't Beta have an O-Ring or Gasket on this Cover honestly??? I RTV'd the Cover to get a decent seal when I put it back together).

The Coil Plate (sorry if this is the wrong term) appears to have the Screws dead centre in the slots...so I'm assuming it's sparking at exactly (or very close to...) TDC. Does anyone have any tips if the timing needs to be adjusted, what's the effect in terms of engine power and response if I advance or retard it? If anyone has a rough guide I'd be very grateful.

I've graduated to the Rev 3 from a 1990 Fantic 307 so you can imagine how much I love this bike...it just needs some fine tuning I'm sure...

[pindie]

I'd google the Beta Carb fix. You may have float issues caused by the retaining pin sliding across and hitting the float bowl casing. You need this - http://www.google.co...pl987H7Mde-OyiQ There are other versions of this with diagrams. My pipes had holes in but the internal parts had never been set right. My 200 does not leak or have issues anymore.

After that I'd worry about timing. Did you put it back as you found it? Mine is slightly to the right of centre by 1-2mm. Lampkins said to me the middle would be ok.

Edited July 20, 2012 by pindie

[copemech]

Ok, I will take a stab at this only because you are likely to find little help with that old bike and configuration.

Pinking- As I recall the timing should be ok in the mid position, as this may indeed be slightly retarded from standard rhich would be the left bias of the slot or right or the screw.

Many bikes in this timeframe were also poorly adapted to more modern pumpgas with possibly less than desireable compression ratios and head designs. Ck your pilot jet size as I figure you may need to go up on it and adjust the fuel trim screw in a bit for low speed. I was running a 38 pilot on my PHBL before I stopped Ping!

The VHST was sold as a fix fir the Mikuni problems and will run it seems, yet not perfect and sensitive to float levels(downhills) variations. Set float arms at 19.5 mm from surface when carb inverted. Go up or down by 0.5mm to find sweet spot.

Hard start- Junk the plug! First symptoms of fouling! Clean all you like , BUT! If it has been fould in transport by not shutting off the fuel or the downhill rich running it is likely toast! I still prefer NGK over any others in standard application, and for $3 they are disposable!

My thoughts, see how you get on!

[pindie]

I agree. NGK all the way. Try the highest octane fuel you can get as well. I use 99ron from the supermarket or shell Vpower. My car needs these types of fuel and the Beta certainly runs sweeter on them.

[carl ekblom]

Pinking might be caused by carbon deposits in the combustion chamber.

I found out that the VHST is sensitive to dirt in the idle jet system. Symptoms will be hard starting, poor running att low throttle openings and..... pinking. I would clean the whole carb, not only the jets but also all drilings and passages in the carb body before trying anything else.

Carl

[pindie]

Carl may have a point if the other "fixes" don't work.

You will need to take the carb to someone with a sonic cleaner. If your local bike does not have one your local mower/chainsaw repair shop might. It'll cost pennies to be cleaned but at least you can rule out any blocked jets or passageways.

[theflyingferret]

Cheers all...

It seems I have a number of things to do and try adjusting.

I'll knock them off one by one and let you know how I get on.

Next trial is this Sunday and all I want is a reliable, well sorted bike to ride it with, I can worry about the outright lack of talent later!....fingers crossed.

[theflyingferret]

Right then...after much tinkering this week here's my baseline:

Timing:

- Advanced 2mm (screw from centre of slot). Was TDC (assumed centre of slot is TDC).

Carb:

- Main Jet #111

- Choke Jet #60

- Idle Jet #S38

- Atomiser #272HH

- Float Level: 40.75mm (from inner casting surface, not the Bowl mating surface as I couldn't measure accurately to that.) Was 40mm.

- Fuel Screw: 1.5 Turns out from stop.

Fuel:

- AvGas 100LL Octane. (local regional airport sold it to me...who knew!) Was running Pump 93 Octane.

Plug:

- Brand new NGK.

I had the Carb completely disassembled. All Jets are the ones that came out of it. All Jets and Passages cleaned with Carb Cleaner and then blown out with compressed air. I didn't see anything particularly dirty or blocked though and I've always run a decent inline Filter.

Started and rode it for the first time this morning.

Starting:

- Still a pig...took about 15kicks and eventually fired with the choke off. Still not sure what's going on here. At least I didn't have to take the plug out and dose the thing.

Running:

- Ran faultlessly in terms of reliability.

- The AvGas seems to have eliminated the pinking completely.

- Altering the float level has done the trick regarding the cutting out going down steep hills. (valve now closes when floats are in a higher position than they were)

- Low end seems fine, it pulled well with no hesitation and response to throttle input was really good.

- Top end. Did a few hill climbs and it seemed to have bags of power and pulled clean.

- Transition between low and top end seemed good to me.

One of the problems I have is that I don't have a good basis for comparison in terms of how it should respond and run. With a big Idle Jet (S38) and small Main Jet (111) you'd think I'd be rich at the bottom end and lean at the top...perhaps good in the middle?!!

The lad I ride with has an '09 Sherco with a 271cc (ish) engine. He's got the same Dellorto but is running a much smaller Idle Jet and bigger Main Jet. I know it's not apples to apples as the engines are very different but you'd think the Jet sizes needed wouldn't be too different. His Sherco's a very well sorted bike and is very good throughout the RPM/load range.

I do have another Dellorto PHBL (came off another friend's Gasser 327cc when he went to Keihen). I don't know what Jet's are in it but you think the Main at least might be bigger than the one I'm running. Perhaps it's worth more experimentation...

I'd appreciate any advice on what you more experienced lads would do from this point. I've got a trial to ride in tomorrow so I'll see how I get on and maybe talk to a few of the Expert class lads and get them to ride it for me.

Thanks again for the previous advice...making progress...

Ferret.

[theflyingferret]

Forgot to mention:

Air Filter:

- It was filthy with mud and dust.

- Thoroughly cleaned, oiled and put back in a Filter Box that was also thoroughly cleaned out.

[pindie]

Have you checked the compression? If you rest your hand on the kick start and slowly press down you should find it hard to turn the engine over. If it is fairly easu your rings (possibly barrel as well) are worn. New rings are easy to do if this is the problem.

You can get some nasty and gimmicky additives to help check for this (or run a 25-1 mix) to see if it improves but it will be smokey. This would confirm worn rings.

[jonnyo]

Hi theflyingferret

First of all sorry for any "bad english" words. I'm swedish.

I've had all your problems with my last bike Beta REV-3 270cc 2000 and fixed them all during the time I owned the bike (3 years). A month ago I sold a perfect working Trial to a supersatisfied guy!

1. Pinking - Make sure that the engine can breathe properly the way it's supposed to do.

My fixes for this (starting at the airfilter):

----------------------------------------------

- New airfilter (the last one had a little crack and was filling the airbox and carb with crap)

- Remove "airbox" and make it superclean inside or you'll be cleaing the carb forever

- Clean carb (again). If it's bad you might have to use ultrasound cleaning. I didn't but I stripped everything from my carb and bathed it in diesel for 24 hours then used compressed air to clean it. One of then channels in the carb had a blocking of one centimeter of carbage in it that came out.

- Replace the reed cage in the intake. The tongues where not sealing a 100% in my case. One of the main reasons for pinking I think.

- Doublecheck the rubberintakes for cracks and replace if necessary

- Plug - NGK between 5 to 7.

- Clean exhaust.

- Make sure exhaust not leaking in joint between exhaust and silencer

- Replace silencer padding (Beta original, not some isolation material from house construction)

- Beta in sweden also gave me a tip changing the then main seals (and main bearings). When the engine gets really hot a old hardened seal will let air get in behind the flywheel. I changed these but can't be sure it made a difference.

Note:

-----

- It takes som running before the engine "get used to the changes"

2. Starting - The carb gets flooded

My fixes for this:

------------------

- Every night make sure the fuel tap is closed (and that it closes a 100%)

Start procedure that worked for me (Observe! Used only for the first start of the day)

1. Open fuel tap

2. Pull the choke up

3. Kick it

4. When it starts, rev the engine a litte then press down the choke. Let it warm a little.

During a day I never shut off the fuel tap and choke. It just started in 1 - 2 kick's

3. Stalling downhill - Carb doesn't flood :-)

I didn't have this exact problem but I sent my Mikuni carb to Beta in sweden and they drilled a new channel in my carb fixing it from flooding (known issue on Mikuni).

I think that the angle of your carb and the adjustment of the valve stopping the fuel from coming into the carb is in "poor harmony". It is flooding when the fuel tap is on and the bike is in a normal angle (giving startproblem) and shutting off when you're going downhill.

Hope I helped.... Jonny Olsson in Sweden (now riding Beta Evo 290cc 2011)

[theflyingferret]

Pindie, I have no reason to suspect the rings are bad or that blowby through the Rings is an issue. Although I haven't pressure tested the cylinder it has plenty of compression and is quite a challenge to kickover, let alone push the kickstart by hand. It seems very happy with it's 67:1 mix of fully synthetic and doesn't smoke at all.

Jonnyo, thanks for passing on your experience of the early Rev3. The pinking is cured, even after I advanced the timing a little, decent octane petrol was what it needed. The downhill stalling seems to cured also, I think lifting the Float arm 0.75mm cured this. These to issues were my biggest concerns and I'm really happy that after a 4hr trial with some serious up and downhill inclines on Sunday I didn't experience either of them.

I haven't had the Reed Cage out of it yet, I'll get to that the next time the Carb comes off. I have no reason to suspect there's an issue but you never know. I do need to re-pack the Silencer, it's on the to-do list.

No reason to think either Crank Seal is leaking either. I'm not using any Gearbox Oil and it's not hunting and over-running like my Fantic does (that does have a dried out leaky Flywheel-side Seal).

I did get lucky at the weekend as we had an ex-Canadian Champ riding in the Expert class. He kindly finished the trial on his 2wk old Ossa and took my bike out for a spin. His feedback was that it wasn't as responsive as it ought to be at the bottom end and that it leaned out at the top. Perhaps he had this impression as he'd just got off his fuel injected wonder-bike!...but this backs up my suspicion that my Idle Jet is a tad too big and the Main is too small. I've ordered 2 different sizes of each to experiment with...I also have the 5 settings on the Needle to add to the mix so there's some work to be done yet.

You're absolutely right about the general behaviour with the bike...shutting off the petrol etc. I do this now whenever I've finished riding the bike and let it run for a while with the tap in the "off" position. It'll run for quite a few minutes like this which is a surprise but this has lead to easier starting from cold...although it floods if I use the choke. Perhaps I need a smaller Choke Jet as well as the Idle.

Thanks lad for the tips, keep them coming and I'll let you know how I get on once I've got the thing re-packed and re-jetted.

Cheers............Ferret.

[copemech]

Not knowing where you are or the ambient temps, the cold start issue becomes more difficult. Seems you have achieved good running for the most part and the only thing I can see from your carb specs would possibly be the 111 main jet. This would allow it to rev cleanly at altitude, but I am thinking something more along the 155-118 line.

Fuel screw seems ok with that low jet,

[theflyingferret]

Well, I've fitted a 116 Main Jet and dropped the Needle one groove so it's right in the middle now. I have a 118 Main to try also if needed.

It has been very hot and humid up here in New York Copemech, I hadn't thought about this too much. We're riding from 300-800m elevation so that's a consideration too.

I'm really hoping that I get this bike nailed soon...at the moment it seems that I have to work on it for 2hrs for every hour I want to ride it. I noticed that the front wheel wasn't turning freely, this turned into a full Caliper strip and rebuild. I quickly tried to start it after I fitted the 116 Main early and it didn't want to know...so frustrating as it ran like a swiss watch throughout the trial last Sunday.

[peterh]

While the following link was written for Mikuni and Keihin carbs (andon Lambretta scooters) I have used it successfully wtih my Beta Evo's having also installed Boyesen Reeds. Some of the same principles will be likely with the Dellorto? I found this process easy to work with rather than diong the throttle chop method (in surburbia).

http://www.smellofdeath.com/lloydy/jetting.htm

Note that the guide starts with the needle clip in the middle position and changes are then made around that starting position. So getting the pilot and needle correct without any influence from the main jet (or making me understand when the main jet circuit was coming into play) worked well for me.

Good luck.