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Post by Bakker RD on Nov 23, 2020 21:19:01 GMT 1
Today I took my Bakker Rd ypvs out for a 25Km test-ride. This, apart from enjoying the nice autumn weather we had today, was also to be able to measure the radiator inlet and outlet temperatures as it is new (and custom made) and I wanted to check its effectiveness. (see post on " radiator upgrade YPVS 31K")
I found the power reasonable but I noticed some hesitation when opening the throttle from 6000rpm. Above 7 grand it picked up but below 7000 that not what I expected.
This low revs hesitation grew worse to the extend that I could barely get away from a traffic light. Idle remained perfect but it needed lots of clutch slipping to move on and only above 7000rpm it moved kind of normal. In the end I was totally unable to get away from standstill and had to push it home. I started it two times in the kilometer I had to walk and both times it ran, idled ok but only a "Blehhhh" when I opened the throttle.
In the garage I removed the fuel line from the tap and found a rather poor flow of fuel coming from the tap. I connected a 50cm piece of fuel line and let it fill a liter bottle which I timed with a stopwatch. The tap delivers one liter of fuel in exactly 3 minutes. This seems fine to me.
I started the now partly cooled down bike (with the correct fuel line reconnected) and all seemed ok. Idle was good and it responded well to throttle inputs but I still can't get off the line. Much like pulling away in third gear.
I removed the filter pods to check if both slides move (I had a broken cable once preventing one slide to move up. This was a real head cruncher as it idled on both cilinders but had no power) and they do move so throttle cable is OK.
Any thoughts before I remove and dismantle the VM34's once again?
Cheers,
William
just removed the plugs. They are a bit oily and wettish
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Post by Shytalk on Nov 24, 2020 6:09:54 GMT 1
The other place to look at is the fuel tank / filler cap is the vent blocked causing low flow after some use.
If you remove the cap when the symptoms are there if it’s a blockage in the vent you should hear an audible gush of air.
Is it possible for you to use an auxiliary fuel tank for a short trip to test?
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Post by Bakker RD on Nov 24, 2020 7:14:00 GMT 1
Fuel tank and tap are good. The tap can be blown trough from the hose end and the vent is good. There is even an auxillary vent besides the vent in the Monza cap.
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Post by midlifecrisisrd on Nov 24, 2020 9:47:23 GMT 1
If it runs over 7k but not under fuel flow to the carbs is not the problem as at 7k it needs a lot more fuel
I'd say your pilot jets are partially blocked
Steve
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Post by Bakker RD on Nov 24, 2020 16:56:54 GMT 1
Pilot jets are the same as the Idle jets right?
In that case they cannot be partially blocked as it has a good idle. But I will remove the carbs anyway to find out if something is wrong. Will check the reeds when the Mikunis are off and if that does not clear something up I will remove the exhausts to have look at the pistons.
Work to do!
William
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Post by stusco on Nov 24, 2020 17:33:54 GMT 1
It will idle with too small pilot/ idle jets or airscrew incorrectly set but when you try to pull away it will bog down unless you get the revs up above 6000rpm,try upping the pilots or even adjusting the airscrews
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Post by Chewie01 on Nov 24, 2020 17:41:52 GMT 1
If I've read this correctly, we know that when it was cold it was OK but when it got hot it won't rev under load at low rpm, but above 7K it's fine. Looking at the carbs makes sense, but I would at least put a meter on the alternator coils to see if the insulation is breaking down.
I'm sure somebody on here will know what the resistance values should read.
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Post by midlifecrisisrd on Nov 24, 2020 17:43:55 GMT 1
Pull the choke and see if it pulls away
Steve
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Post by jessy03 on Nov 24, 2020 18:22:25 GMT 1
As said I think I would try some bigger pilots
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Post by headcoats on Nov 24, 2020 18:33:23 GMT 1
Is there someone else on here with VM34's just to get a bit of input ?
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Post by stusco on Nov 24, 2020 18:39:04 GMT 1
Just reading your old threads its been running recently so not just rebuilt so for me it’s either the stator or pilots the stator is easy to check first
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Post by marrcel on Nov 24, 2020 19:13:53 GMT 1
What was the meteo Willem?
Can it be carb freece? This occurs especialy with small throttle opening. The large pressure drop of the mixture can freeze the moist out of the air and this blocks channels in carbs.
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Post by Bakker RD on Nov 24, 2020 21:22:01 GMT 1
The weather was fine. 12 deg C and sunny. It ran ok for at least 20Km's. I noticed a flat spot at arounf 6 grand but not enough to bother me. After thgose 20Km's I noticed pour low end torque and difficult accelerating from walking pace (traffic) and traffic lights.
Finally crazy clutch slipping was needed to get it moving and it picked up only at around 8000 revs. When stuck again in traffic and having to give her the same punishment to get moving again I decided to stop and walk her home.
Trying the same with choke on gave no improvement.
I have checked so far:
Fuel tap. Clear and supplying 1 liter in 3 mins.
Tank ventilation. Both openings open.
Fuel filter: (almost) clean. But fitted a new one just to be sure
Plugs. OK
Throttle cable: OK
Slides: moving
Carburators: removed and cleaned and jets cleaned with compressed air. No blockage found. (pilot jets 55. Main 330)
Checked V-force 3 reeds : seem Ok
Air screws : 1.5 turn open. reduced to 1.25 turn.
Tomorrow test ride.
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Post by marrcel on Nov 24, 2020 22:28:56 GMT 1
That remembers me. Last year @ 6krpm my pv was running lean on the needle and got overheated. Yes hole in piston. I don’t wanna scare you but the same simptomes.
So Check compression first. And use a boroscope. I hope it is ok for you.
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Post by Tobyjugs on Nov 24, 2020 22:35:14 GMT 1
Can you feel you have compression when you kick it over.
Did you look at your pistons through the exhaust ports.
Do both carbs have tickover screws and synched correctly
Oh I type too slowly.
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Post by Bakker RD on Nov 25, 2020 19:51:05 GMT 1
Just came back from a test ride. All seems OK. In fact it pulls stronger from down below than it did during the first few miles of my previous ride. Must have been partly blocked pilot jets after all. This test ride was only 2.5 Km's but long enough to know there is no big mechanical issue.
thanks everybody for their help and advice. it is a great forum!
I have only one head cruncher left and that is the Scitsu tacho but that will be another thread;-)
Cheers,
William
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Post by steeley on Nov 26, 2020 11:09:26 GMT 1
Hi , just had a look at a pair of carbs i have in my shed . I have not used them myself, 34mm but bought them about 20years ago from a chap who ran them on a 350lc. Pilot jet 70 main jet 300 needle jet 0-2 needle 6f9 .
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Post by Bakker RD on Nov 27, 2020 12:39:54 GMT 1
Can you feel you have compression when you kick it over. Did you look at your pistons through the exhaust ports. Do both carbs have tickover screws and synched correctly Oh I type too slowly. I have installed an idle adjustment screw in the Rh carburator. This wasn't there. It was a bit of a challenge as the Idle set screw provision on the RH side of the carb body had to be drilled and threads tapped to fit the screw (M6 fine thread). Also the slide itself needs to be modified to create a ramp for the screw and with that a safety problem arose with the slide. Both slides have a guide for a tiny pin located on the RH side of the carb body and the machined ramp for the Set-screw cuts into this guide. Causing.... the risk of the slide not being able to close from full throttle as the guide pin might be out of its location. Not something you want. To fix this I fitted a guide pin to the LH side of the carb body (provision is cast in, just need drilling with 1.5mm and fitting of a suitable metal pin.) and machined a narrow guide in the slide on the LH side, mimicking the guide in the RH side. This removed the risk. I have set both slides with a drill bit. marked the set screws and set that equally. This method gives a much better initial gas responce. |
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Post by Tobyjugs on Nov 27, 2020 16:06:42 GMT 1
Famous last words to say drill and tap the blanking. All the hard work has paid off.
Such a lovely bike Willem
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Post by Bakker RD on Nov 27, 2020 17:29:24 GMT 1
Grazie Mille Tony!
Few things left to do. Get the Tacho to work. Calibrate or replace the Motometer watertemp gauge. Test the water circulation system and tidy up the cosmetics a bit (paint chips and the like).
And new tires. The current tires, with just 200Km on them are 2008 Pirelli demons and they are now even harder than they were when new. The thing is that the tyre choice is very limited. Currently only the BT45 and the Pirelli Demon are available in 100/90-16 and 120/80-18
Cheers,
william
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