Carb adjustment GV250
- This topic has 11 replies, 2 voices, and was last updated 3 years, 6 months ago by
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Posts
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Hi everyone. Well, at long last I have my bike on the road! But I need advice with possible carb adjustment.
The bike starts beautifully with a bit of choke, which can be turned off after just a couple of minutes. Out on the road for the first time, it rans fine until I opened the throttle to give it a bit of wellie! Then it seems to choke. When I got back, with the engine obviously warm and no load, the revs shot up without problem.
I have the larger jets and new needles from Marcel. What can I do? As soon as I get time I will look at the plugs to check colour, but if anyone has an idea please tell me!
Here are first pics of bike.
dav 
cof 
cof 
dav -
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Hi Marcel. I said choke not chock!! The rpm stalls at about 4000. Unfortunately, I live in the country and the roads are appalling! I couldn’t do much and there aren’t any strait bits, so I didn’t notice speed, but in 3rd it just stopped accelerating at about 4000. I can’t go out on main roads as I don’t have an ITV (MOT) yet.
Does that help?
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I meant “choke/chock” (english is weird) as in , if you ride faster , the bike feels like its being strangled by its neck.
That would be your carb slides fella , they should be freely moving up and down , without so much as a disturbance intheir cylinder walls of the carb unit
Though around 4k – 7k rpm is slide territory , after 8k ish , they should be fully lifted , drinking main jet fuel.
Take a look at this video, it is “exactly” how our carbs behave based on situation and throttle action.
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Thanks Marcel, great video! Would your diagnosis be correct even though with no load, in neutral, it revs perfectly?
it is what one of our GV donor’s did, the carb was being a nuisance so had to reset the whole thing and re-do it all up, in fairness , it also needed engine clearances doing as last owners didn’t treat it well.
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Not running well! I’m not sure if it’s running on 2 cyls!! The front pipe doesn’t seem as hot as the back one.
I would be grateful if someone could post a sound byte here of a 250 at idle, and snap the throttle open to high revs, so I can compare the sound and speed of revs rising, to mine. I don’t know if it could be because of the possibly blocked idle jet on the font cyl.
Waiting!
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Front = Rich , or ignition coil or ignition cap is wanning.
Rear = Rear cylinder jet may be blocked in full throttle , or slide NEEDLE is on lean setting or , plug is wanningClean the spiral threads of the plugs , or get new ones CR8E stock, then go for a little short test , take them out.
= If the plug threads are wet with oil, there could be an internal head leak to do with gaskets or valve seals
= If the plug threads are dry BUT ….all threads are dark = bike is overheating a tiny bitThe threads should be totally dry leaving on about 3-4 lines of thread dark , this would be acceptable and normal.
Hope this helps, will check your email shortly as i did get it but i was away for a day , my apologies!
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Marcel, what is “wanning�
the process of decreasing, declining, or coming to an end
The dictionary explained it better than i would lol.
And yes email sent , check your inbox now sir
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- You cannot reply to this topic.
- This topic has 11 replies, 2 voices, and was last updated 3 years, 6 months ago by .
-
Posts
-
-
Hi everyone. Well, at long last I have my bike on the road! But I need advice with possible carb adjustment.
The bike starts beautifully with a bit of choke, which can be turned off after just a couple of minutes. Out on the road for the first time, it rans fine until I opened the throttle to give it a bit of wellie! Then it seems to choke. When I got back, with the engine obviously warm and no load, the revs shot up without problem.
I have the larger jets and new needles from Marcel. What can I do? As soon as I get time I will look at the plugs to check colour, but if anyone has an idea please tell me!
Here are first pics of bike.
dav cof cof dav -
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Hi Marcel. I said choke not chock!! The rpm stalls at about 4000. Unfortunately, I live in the country and the roads are appalling! I couldn’t do much and there aren’t any strait bits, so I didn’t notice speed, but in 3rd it just stopped accelerating at about 4000. I can’t go out on main roads as I don’t have an ITV (MOT) yet.
Does that help?
-
I meant “choke/chock” (english is weird) as in , if you ride faster , the bike feels like its being strangled by its neck.
That would be your carb slides fella , they should be freely moving up and down , without so much as a disturbance intheir cylinder walls of the carb unit
Though around 4k – 7k rpm is slide territory , after 8k ish , they should be fully lifted , drinking main jet fuel.
Take a look at this video, it is “exactly” how our carbs behave based on situation and throttle action.
-
-
Thanks Marcel, great video! Would your diagnosis be correct even though with no load, in neutral, it revs perfectly?
it is what one of our GV donor’s did, the carb was being a nuisance so had to reset the whole thing and re-do it all up, in fairness , it also needed engine clearances doing as last owners didn’t treat it well.
-
Not running well! I’m not sure if it’s running on 2 cyls!! The front pipe doesn’t seem as hot as the back one.
I would be grateful if someone could post a sound byte here of a 250 at idle, and snap the throttle open to high revs, so I can compare the sound and speed of revs rising, to mine. I don’t know if it could be because of the possibly blocked idle jet on the font cyl.
Waiting!
-
-
-
Front = Rich , or ignition coil or ignition cap is wanning.
Rear = Rear cylinder jet may be blocked in full throttle , or slide NEEDLE is on lean setting or , plug is wanningClean the spiral threads of the plugs , or get new ones CR8E stock, then go for a little short test , take them out.
= If the plug threads are wet with oil, there could be an internal head leak to do with gaskets or valve seals
= If the plug threads are dry BUT ….all threads are dark = bike is overheating a tiny bitThe threads should be totally dry leaving on about 3-4 lines of thread dark , this would be acceptable and normal.
Hope this helps, will check your email shortly as i did get it but i was away for a day , my apologies!
-
-
Marcel, what is “wanning�
the process of decreasing, declining, or coming to an end
The dictionary explained it better than i would lol.
And yes email sent , check your inbox now sir
-
- You cannot reply to this topic.