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Post by buzz on Sept 9, 2018 8:08:19 GMT -5
When I open up the throttle on my Derbi Senda it runs rough until the revs build up and then it starts to run right.So in first and second gear it is slow and rough until the revs build.I have adjusted the carb, it has a new throttle cable and new spark plug.
Any suggestions gratefully received.
Buzz.
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Post by pistonguy on Sept 9, 2018 17:34:57 GMT -5
Ok lets get some detailed information.
Two Stroke correct?
How much time or miles on her?
What kind of Two Stroke oil are you using and were do you put it?
When you say adjusted the Carb, the Idle mix screw?
I believe she has Fixed Jets and she sounds Fat on the bottom end and mid range. all garbled up with fuel until she clears up on the top end..
Can you take a picture of the Spark Plug color for us? please.
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Post by buzz on Sept 12, 2018 2:44:21 GMT -5
I adjusted the mixture screw by winding it in full and then out 2.5 turns. When the Derbi revs click in it runs at 95kph and is sweet. It's the initial start off that is rough, I took out the spark plug and it is not oiled up and quite clean, the colour is white.I wondered if it is the ht cap or lead.
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Post by buzz on Sept 12, 2018 9:33:24 GMT -5
I adjusted the mixture screw by winding it in full and then out 2.5 turns. When the Derbi revs click in it runs at 95kph and is sweet. It's the initial start off that is rough, I took out the spark plug and it is not oiled up and quite clean, the colour is white.I wondered if it is the ht cap or lead. The oil I am using is Total Hi Perf 2T. |
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Post by buzz on Sept 12, 2018 11:14:19 GMT -5
When I say the plug is white I meant it is oil free .
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Post by pistonguy on Sept 12, 2018 22:26:13 GMT -5
Ok a White plug is indicating a Lean condition.
You may have a air leak..
How many miles on the bike?
How well does the bike start from cold? good? bad? take awhile or?
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Post by buzz on Sept 13, 2018 3:34:57 GMT -5
Not sure of the mileage it's a 1999 Senda Evo, it starts first kick every time. My son gave me wrong info on the plug. I have tried to upload an image of the plug, given up.
The plug is black on the tip but not oily or encrusted.
If I hold the throttle slightly open and let the revs build it will gradually start to run correctly i.e. sing.
When it takes off in first and then go into second and you hold it in second the revs will build and then it starts to run and sound correct.
Thanks,
Ed.
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Post by pistonguy on Sept 13, 2018 8:13:04 GMT -5
Im having bit of trouble determining if she is a Piston Port or Reed Valve motor.
Im thing Reed Valve.
Check them, hers how they work and how to check them
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Post by cyborg55 on Sept 13, 2018 8:23:03 GMT -5
I was thinking a cracked or chunked reed myself
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Post by buzz on Sept 13, 2018 9:11:27 GMT -5
Looking at where the carb is attached to the cylinder there is a four screw plate, am I right in thinking this is the reed valve. If so I will order a new one somehow, the problem with Senda's are their are two many models to choose from.
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Post by buzz on Sept 13, 2018 10:28:02 GMT -5
Sorry the bike is a Derbi Senda SM 2009 , It belongs to my son so of course I am MR fixit.
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Post by pistonguy on Sept 13, 2018 10:32:53 GMT -5
Looking at where the carb is attached to the cylinder there is a four screw plate, am I right in thinking this is the reed valve. If so I will order a new one somehow, the problem with Senda's are their are two many models to choose from. Yes pull off that Four Screw plate and the Reed Cage is behind there. |
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Post by buzz on Sept 13, 2018 12:58:59 GMT -5
Thanks for your help, I will keep you posted.
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Post by cyborg55 on Sept 14, 2018 10:16:34 GMT -5
Any results?
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Post by buzz on Oct 7, 2018 6:39:58 GMT -5
Hi it's Ed for Buzz,
I changed the reed valve for my son and at first it was a little better by now it is the same. It is in the local moto place for some electrics and I asked the mechanic what he thought was the problem, he said there was lack of compression in the bike.
Do you think this could be the problem?
I have been around the engine and carb with soapy water to see if there were any air leaks but could not find any.
It is still rough and slow on the initial start but then as the revs build the whole engine tone changes and it goes well, gets up to about 95k.
I will see the mechanic on Tues to pick up the bike and ask him more.
I would be grateful for your opinion as I cannot afford to spend money where I don't need to.
Many thanks
Ed.
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