Gord
Drag-strip hero
Posts: 233
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Post by Gord on Aug 7, 2021 2:20:59 GMT 1
My rebuilt engine starts up and idles but stalls or has little to no power when the throttle is applied. I think it might be debris behind the brass balls which I am hesitant to remove. The carbs have been vapour blasted and am thinking that may have bunged up. I have sprayed carb cleaner through all accessible passages. I have a spare carb and noticed the spare has a small brass down tube that the bikes carbs don’t have. Its seems to be in a blind hole but can’t tell for sure. Any thoughts would be greatly appreciated. This is a spare carb  Original bike carb:  |
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Post by dusty350 on Aug 7, 2021 9:05:40 GMT 1
Hi mate, If I were you, I would get the brass balls out and then put through the ultrasonic. When I've done it on rebuilds, they are nearly always blocked, and that will affect the running, without doubt. Years ago, I sent a pair of Rd400 carbs to a well known member on another forum who did carb refurbs. They came back looking mint, but I found a small amount of blast media in a float bowl. I thought that odd so decided to pop the emulsion tubes out. They were absolutely full of blasting media ! He hadn't stripped them to clean them, hence the fine media had gotten everywhere. Took me some time to remedy them. The brass ball removal is fiddly rather than difficult, but well worth the "ball" ache ! Dusty  |
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Post by tony2stroke on Aug 7, 2021 9:39:51 GMT 1
The brass pipe you circled is the choke pick up, the choke won't work without it.
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Post by jon on Aug 7, 2021 9:51:31 GMT 1
The brass pipe you circled is the choke pick up, the choke won't work without it. I initially thought that, but isn’t that a right hand carb? Not got one to hand at present to see. Maybe image is inverted? 🤷♂️ Jon |
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Post by tony2stroke on Aug 7, 2021 11:42:25 GMT 1
The brass pipe you circled is the choke pick up, the choke won't work without it. I initially thought that, but isn’t that a right hand carb? Not got one to hand at present to see. Maybe image is inverted? 🤷♂️ Jon Looking at the pics they are both same side, but as you say pic may be inverted, only the left carb with the choke pull on has that pipe, the right side doesn't have it. You can buy some 3mm diameter brass modelling tube on ebay and fit a new tube to the carb, I have done this myself, the hardest part is drilling the holes in the side of the tube, then just tap it in to the carb body with a screwdriver handle. |
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Post by jon on Aug 7, 2021 12:55:14 GMT 1
I initially thought that, but isn’t that a right hand carb? Not got one to hand at present to see. Maybe image is inverted? 🤷♂️ Jon Looking at the pics they are both same side, but as you say pic may be inverted, only the left carb with the choke pull on has that pipe, the right side doesn't have it. You can buy some 3mm diameter brass modelling tube on ebay and fit a new tube to the carb, I have done this myself, the hardest part is drilling the holes in the side of the tube, then just tap it in to the carb body with a screwdriver handle. Look at the 2 stroke oil I feed and the tickover screw. Both should be on the outside so it suggests a right hand carb someone has put a tube in?! As said unless the picture is inverted? Jon |
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Post by tony2stroke on Aug 7, 2021 13:39:24 GMT 1
Looking at the pics they are both same side, but as you say pic may be inverted, only the left carb with the choke pull on has that pipe, the right side doesn't have it. You can buy some 3mm diameter brass modelling tube on ebay and fit a new tube to the carb, I have done this myself, the hardest part is drilling the holes in the side of the tube, then just tap it in to the carb body with a screwdriver handle. Look at the 2 stroke oil I feed and the tickover screw. Both should be on the outside so it suggests a right hand carb someone has put a tube in?! As said unless the picture is inverted? Jon Yes agree Jon, odd to say the least. |
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Gord
Drag-strip hero
Posts: 233
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Post by Gord on Aug 7, 2021 14:19:09 GMT 1
I initially thought that, but isn’t that a right hand carb? Not got one to hand at present to see. Maybe image is inverted? 🤷♂️ Jon Looking at the pics they are both same side, but as you say pic may be inverted, only the left carb with the choke pull on has that pipe, the right side doesn't have it. You can buy some 3mm diameter brass modelling tube on ebay and fit a new tube to the carb, I have done this myself, the hardest part is drilling the holes in the side of the tube, then just tap it in to the carb body with a screwdriver handle. You're correct the carb without the tube is the right side, and my spare is a left.....I hadn't thought of that. The choke works so must be installed on the left one ( I haven't pulled it apart yet). Thanks!! |
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Gord
Drag-strip hero
Posts: 233
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Post by Gord on Aug 7, 2021 14:21:46 GMT 1
Hi mate, If I were you, I would get the brass balls out and then put through the ultrasonic. When I've done it on rebuilds, they are nearly always blocked, and that will affect the running, without doubt. Years ago, I sent a pair of Rd400 carbs to a well known member on another forum who did carb refurbs. They came back looking mint, but I found a small amount of blast media in a float bowl. I thought that odd so decided to pop the emulsion tubes out. They were absolutely full of blasting media ! He hadn't stripped them to clean them, hence the fine media had gotten everywhere. Took me some time to remedy them. The brass ball removal is fiddly rather than difficult, but well worth the "ball" ache ! Dusty Thanks Dusty, I tried removing the ball on the spare one and it was pretty simple get out. Do use any adhesive when putting them back in or rely on the press fit only? I was thinking about using Triple Bond (just a tiny amount). |
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Post by midlifecrisisrd on Aug 7, 2021 15:25:43 GMT 1
I drop a little thread lock onto the ball then turn back upside down to stop any chance of it making its way behind the ball
Steve
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Post by dusty350 on Aug 7, 2021 15:47:08 GMT 1
I do the same Steve , just a little low strength threadlock
Dusty
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Post by zig on Aug 20, 2021 22:13:15 GMT 1
I do the same Steve , just a little low strength threadlock Dusty Hi Dusty the brass ball removal is also a 'to do' on both 250/350lc carbs ? and it's the large ball Dusty , present on both carbs?? ZiG |
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Post by reedpete on Aug 21, 2021 5:03:33 GMT 1
The large brass ball positioned at 6 o’clock is present on all RD 250/350/400 AC and LC , YPVS carbs from the 1975 onwards.
It blanks off the original passage on the earlier carbs that feed the air correction jet. The reason for introduction was that at that location the air correction circuit was found to get compromised by 2T oil that pooled in the bottom of the track if the engine wasn’t running often at full chat.
Unfortunately the ‘fix’ created several other problems. One of which is that by diverting the feed via a rather convoluted drilling labyrinth a dust trap was formed. So rather than getting clogged with oil, it then became , after extended service, clogged with dust....and the ‘famous’ balls out process was born.
Ironically, the best/real solution didn’t appear until the carbs on the TZR, more that a decade later......and the solution was....move the air correction passage from 6 o’clock to 4 o’clock and have it open directly to the mouth of the carb as it was always intended to be ....no balls required!
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