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Post by yamnewbie on Jun 3, 2021 7:42:41 GMT 1
Hi
My 250LC will happily pull the red line up to 4th gear but wont pull in 5th 6th gear i.e will do 75 in 4th but change to 5th it starts slowing down so wont sit at a constant speed on dual carrigway. Any ideas what may be the problem.
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Post by midlifecrisisrd on Jun 3, 2021 8:23:51 GMT 1
First check it hasn't got 350 gearing on it
Secondly you need to do a compression check which I suspect will be low
Steve
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Post by yamnewbie on Jun 3, 2021 8:34:20 GMT 1
Done a compression test 108 psi in both cylinders. Havnt checked the gearing,but the bike has got a 350 rear wheel on it. What gearing should be on a 250.
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Post by midlifecrisisrd on Jun 3, 2021 8:37:02 GMT 1
Think 250 will be 16/41
350 17/39
Steve
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Post by 29davyt on Jun 3, 2021 8:55:13 GMT 1
As Steve says, check the gearing.. it’s not a restricted German bike is it or got the exhausts off one ??
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Post by tony2stroke on Jun 3, 2021 10:19:47 GMT 1
Gearing for 250 is 16 front and 41 rear as Steve said, also as 29davyt said check you don't have restricted exhausts and carbs from the restricted version, easy to find out, exhausts should start with 4L0, if 4L2 they are restricted, and carbs should be 4L1, if 4L2 they are restricted, if you have both, then the bike will be way down on power.
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Post by liffy16 on Jun 3, 2021 10:43:50 GMT 1
Just rag it in every gear,not really it's thing cruising, well mine doesn't like cruising and if it drops below about 7ish I have to drop a gear anyway with the correct gearing
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Post by yamnewbie on Jun 3, 2021 13:21:35 GMT 1
Gearing for 250 is 16 front and 41 rear as Steve said, also as 29davyt said check you don't have restricted exhausts and carbs from the restricted version, easy to find out, exhausts should start with 4L0, if 4L2 they are restricted, and carbs should be 4L1, if 4L2 they are restricted, if you have both, then the bike will be way down on power.
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Post by yamnewbie on Jun 3, 2021 13:23:02 GMT 1
Its a Uk bike, carbs and exhaust are all correct.
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Post by abar121 on Jun 3, 2021 14:17:44 GMT 1
Have you taken the balls out and totally stripped / cleaned the carbs? Check all the jets are original and not copies.
How do the plugs look? Put a different kind of plugs in your ears and try it briefly with the baffles removed. I though I'd thoroughly cleaned the pipes on my H1, but a bit of carbon loosened up on the first ride and made one pot run poorly. Took forever to sort out until someone suggested removing the baffles to check.
Next step would be a leak down test, then stator, coils, cdi etc.
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Post by stusco on Jun 3, 2021 14:59:48 GMT 1
Yeah choked baffles caught me out back in the day on a gp100, stripped it new rings cleaned the carb set it up still crap spoke to the local bike shop (C&j Wilson in uphall) they said baffles but we had to cut the exhaust in half to get them out ,put it all back together and it was a flying machine (for a gp100)
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Post by yamnewbie on Jun 3, 2021 17:10:53 GMT 1
Done a compression test 108 psi in both cylinders. Havnt checked the gearing,but the bike has got a 350 rear wheel on it. What gearing should be on a 250.
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Post by yamnewbie on Jun 3, 2021 17:16:41 GMT 1
Think 250 will be 16/41 350 17/39 Steve Thanks for the info, my bike has got 17 -39 gearing on it, so like you said probably some way to it not pulling 5th and 6th gears to well. I will change it to 16-41 and with any luck will sort the problem. My bike has a 350 wheel fitted to it does the 250 and 350 sprockets fit both wheel.
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Post by oldelsieboy on Jun 3, 2021 17:24:37 GMT 1
Think 250 will be 16/41 350 17/39 Steve Thanks for the info, my bike has got 17 -39 gearing on it, so like you said probably some way to it not pulling 5th and 6th gears to well. I will change it to 16-41 and with any luck will sort the problem. My bike has a 350 wheel fitted to it does the 250 and 350 sprockets fit both wheel. No, the bolt pattern is different OEB
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Post by yamnewbie on Jun 3, 2021 18:56:59 GMT 1
Thanks for the info, my bike has got 17 -39 gearing on it, so like you said probably some way to it not pulling 5th and 6th gears to well. I will change it to 16-41 and with any luck will sort the problem. My bike has a 350 wheel fitted to it does the 250 and 350 sprockets fit both wheel. No, the bolt pattern is different OEB
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Post by yamnewbie on Jun 3, 2021 18:58:53 GMT 1
Thanks I pressume I can get a rear 41tooth sprocket to fit a 350 wheel and the front sprocket fits both 250 and 350.
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Post by oldelsieboy on Jun 3, 2021 19:34:31 GMT 1
Thanks I pressume I can get a rear 41tooth sprocket to fit a 350 wheel and the front sprocket fits both 250 and 350. I assume you can but may have to be a special order, try B&C EXPRESSOEB
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Post by tony2stroke on Jun 3, 2021 20:20:39 GMT 1
You could put a 15 tooth front sprocket on and keep the 39 rear, 1 tooth less on the front same as going up 3 teeth on the rear as a rule of thumb, so putting a 15 front will effectively be the same as adding 1 tooth to the rear, making it more like 16 front and 42 rear, better acceleration than standard gearing by 1 tooth extra on the rear, hope that makes sense to you. www.ebay.co.uk/itm/132231043937?hash=item1ec9959b61:g:HTQAAOxyZqhRhhgv
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Post by yamnewbie on Jun 4, 2021 5:05:20 GMT 1
You could put a 15 tooth front sprocket on and keep the 39 rear, 1 tooth less on the front same as going up 3 teeth on the rear as a rule of thumb, so putting a 15 front will effectively be the same as adding 1 tooth to the rear, making it more like 16 front and 42 rear, better acceleration than standard gearing by 1 tooth extra on the rear, hope that makes sense to you. www.ebay.co.uk/itm/132231043937?hash=item1ec9959b61:g:HTQAAOxyZqhRhhgvI have now ordered a 15front sprocket and 39 rear, what size chain do I need.
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Post by abar121 on Jun 4, 2021 9:22:29 GMT 1
You could put a 15 tooth front sprocket on and keep the 39 rear, 1 tooth less on the front same as going up 3 teeth on the rear as a rule of thumb, so putting a 15 front will effectively be the same as adding 1 tooth to the rear, making it more like 16 front and 42 rear, better acceleration than standard gearing by 1 tooth extra on the rear, hope that makes sense to you. www.ebay.co.uk/itm/132231043937?hash=item1ec9959b61:g:HTQAAOxyZqhRhhgvI have now ordered a 15front sprocket and 39 rear, what size chain do I need. That should do the job, assuming it doesn't rub anything. You might have to take a link out. Stock 350 17/39 gearing is at 5.5k at 70mph. Stock 250 16/41 6.2k at 70mph 15/39 6.3k at 70mph. Or to put it another way, 15/39 in top will be slightly shorter than 5th with your current 350 gearing.
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Post by oldelsieboy on Jun 4, 2021 9:32:06 GMT 1
I have now ordered a 15front sprocket and 39 rear, what size chain do I need. That should do the job, assuming it doesn't rub anything. You might have to take a link out. Stock 350 17/39 gearing is at 5.5k at 70mph. Stock 250 16/41 6.2k at 70mph 15/39 6.3k at 70mph. Or to put it another way, 15/39 in top will be slightly shorter than 5th with your current 350 gearing. Standard 350 gear ratio is 16/39 OEB
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Post by tony2stroke on Jun 4, 2021 9:52:11 GMT 1
The standard chain should be OK, although as Abar121 said, you may need to take a link out.
Though if I were you I would just have ordered the 15 tooth front, just to try it and see if you are happy with the extra tooth in the rear so to speak, or whether you want to put a 250 rear wheel on to get back to standard, after all there is someone out there screaming for a 350 back wheel, plus they are more expensive than the 250 wheel, the 250 rears are readily available cheaply, no real advantage to having a 350 rear on the 250 IMO.
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Post by abar121 on Jun 4, 2021 9:57:25 GMT 1
That should do the job, assuming it doesn't rub anything. You might have to take a link out. Stock 350 17/39 gearing is at 5.5k at 70mph. Stock 250 16/41 6.2k at 70mph 15/39 6.3k at 70mph. Or to put it another way, 15/39 in top will be slightly shorter than 5th with your current 350 gearing. Standard 350 gear ratio is 16/39 OEB OK thanks, makes more sense. I took the 17/39 from a quote above. So Stock 350 16/39 gearing is at 5.9k at 70mph. Stock 250 16/41 6.2k at 70mph 15/39 6.3k at 70mph.
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Post by yamnewbie on Jun 13, 2021 14:42:59 GMT 1
Hi all.
Well my bike had a 17 and 39 sprockets on it, put new chain and sprockets on it dropping the front sprocket to a 15, the bike now pulls like a train (for a 250) and now cruises at 70mph in Top gear no problem, also lifts the front wheel in first with a bit of perswasion.
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tommo
Drag-strip hero
Posts: 279
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Post by tommo on Jun 13, 2021 14:50:12 GMT 1
great spelling
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Post by jon on Jun 13, 2021 15:04:39 GMT 1
Do you mean ‘Great spelling, and grammar?’ Jon
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Post by yamnewbie on Jun 13, 2021 15:46:42 GMT 1
Do you mean ‘Great spelling, and grammar?’ Jon [br Comments from people about other peoples spelling and grammer,actually puts people like me from posting. You shouldnt judge people or take the piss when you dont realy know them or what problems they may have in life.
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Post by jon on Jun 13, 2021 16:40:54 GMT 1
To me, your comment on the misspelling of the word ‘ perswasion ‘ was aggressive to those who do have problems with the English language.
I’m on your side by the sound of it? Look at the smilee at the end to show intention.
In fact the instigator of the site Norbo has spelling problems, as far as I know? But what does that matter?
Jon
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Post by yamnewbie on Jun 13, 2021 17:32:55 GMT 1
Not realy sure how my mis spelling or grammer has offended anyone, it was me who felt i was being taken the piss out off, all I was trying to do was tell people that the problem with my bike was sorted. I dont want to offened anyone.
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Post by oldbritguy on Jun 13, 2021 22:05:13 GMT 1
Hi all. Well my bike had a 17 and 39 sprockets on it, put new chain and sprockets on it dropping the front sprocket to a 15, the bike now pulls like a train (for a 250) and now cruises at 70mph in Top gear no problem, also lifts the front wheel in first with a bit of perswasion. Glad you got the gearing sorted at last. Nothing feels as good as getting to the bottom of an annoying problem and getting a great outcome through frustration, trial and error. Top job John 🙂
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