Author Topic: RD250D bogging downon runs - must be fuel ?  (Read 674 times)

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Online Gr8uncleal

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #15 on: May 11, 2022, 04:39:01 PM »
You could well be right, Mally.

I'm not sure how many versions of the coffin tank cap there are. I've seen ones with three screws and others with three rivets, although three screws might just be where someone has just drilled out the rivets and replaced with screws!  :o :D The Daytona tank cap is slightly longer than the earlier versions. I've also seen the cap gasket with and without holes.

The earlier 250/350 gaskets certainly need the holes.
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Offline Mally

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #16 on: May 11, 2022, 05:33:04 PM »
You could well be right, Mally.

I'm not sure how many versions of the coffin tank cap there are. I've seen ones with three screws and others with three rivets, although three screws might just be where someone has just drilled out the rivets and replaced with screws!  :o :D The Daytona tank cap is slightly longer than the earlier versions. I've also seen the cap gasket with and without holes.

The earlier 250/350 gaskets certainly need the holes.

Yeah Al that sounds right ,I wasn't sure , saw many posts on this subject. Noticed the photo posted by Jools looked the same as my cap, and being a 250D also like mines ,could see where he could be going wrong looking for a hole in the rubber seal. Being Yamaha and an old RD anything could be fitted and being a 250D doesn't
necessarily mean its got a 250D cap   ;D
Kawasaki Z900 A4 , 1976
Yamaha R6, 1999
Yamaha RD 250 D, 1977
Raleigh Chopper Mk2 , 1976

Offline robrd

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #17 on: May 11, 2022, 06:30:47 PM »
What would the point be in putting a hole in the rubber seal? the seal is there to stop the petrol leaking out when being sloshed about, if it had a hole it could cause a leak. The hole in the metal part of the cap is definitely the breather hole, it doesn't go straight through the top of the cap but takes air in through the sides, this way it doesn't leak.

Offline joolsuk

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #18 on: May 11, 2022, 06:58:48 PM »
I see now. Mine is the same as your new one.
The hole I the central metal part.

plan:
Blow out that tank cap (with my diving cylinders )
test
Any failure I'll remove the 2 in line fuel filters.

p.s when it bogs down it will eventually stop. If
I leave for a few minutes ots fine again for possible
10 miles. so odd.

p.s your z900 Kwak raised both my eyebrows !
1977 RD250D (mechanical restore)
1980 GS550E
1982 GPZ750R1 (Restore)
1980 GSX250E (mechanical restore)
2002 Stihl FS55 Strimmer (mechanical restore)

Offline betty foRD

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #19 on: May 11, 2022, 07:49:15 PM »
What would the point be in putting a hole in the rubber seal? the seal is there to stop the petrol leaking out when being sloshed about, if it had a hole it could cause a leak. The hole in the metal part of the cap is definitely the breather hole, it doesn't go straight through the top of the cap but takes air in through the sides, this way it doesn't leak.

Round tank seal is different… the air path goes through the rubber. Not a direct path so fuel can’t slosh out but if it’s missing… it doesn’t work. Well documented elsewhere on here.
Rev 'em till they rattle

Offline joolsuk

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #20 on: May 11, 2022, 08:07:56 PM »
p.s my rd250d is standard !!! original !!!!
no odd bits on it !!

so is my standard original tank cap OK?
I assume it is as per my pic of it I posted
and no need to alter the rubber seal ?
« Last Edit: May 12, 2022, 09:46:35 AM by joolsuk »
1977 RD250D (mechanical restore)
1980 GS550E
1982 GPZ750R1 (Restore)
1980 GSX250E (mechanical restore)
2002 Stihl FS55 Strimmer (mechanical restore)

Offline Mally

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #21 on: May 12, 2022, 05:03:15 PM »
So is my RD , all original apart from Allspeeds fitted. I would say your cap is original , its like mine for a 250D. No need to add any extra holes to the tank cap, mine ran ok ( in bits now for full resto) and will again without any mods to the fuel cap. I think if it blows thro clear then I don't think that is your problem, if it persists after that.

Here's a photo of the Z900 after resto for you, I've owned it and ridden it from 78 to this day, cheers mate.
Kawasaki Z900 A4 , 1976
Yamaha R6, 1999
Yamaha RD 250 D, 1977
Raleigh Chopper Mk2 , 1976

Offline joolsuk

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #22 on: May 14, 2022, 06:49:54 AM »
z900:
What a simply awesome bike that is.
That and a RD !

Update:
Tank cap off while bogging down was
present and no effect. Its not the cap.
The cap is def original as I have owned
my RD since 1980.

- inline fuel filters off

2m run no issues but not long enough to
be sure. Indeed need a 15 miler.
1977 RD250D (mechanical restore)
1980 GS550E
1982 GPZ750R1 (Restore)
1980 GSX250E (mechanical restore)
2002 Stihl FS55 Strimmer (mechanical restore)

Offline Mally

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #23 on: May 14, 2022, 08:35:12 AM »
Thanks mate, it’s good to hear of what I hope is a resolution to your problem , some threads never get to a reply to give a result to the input given by members to help out another, fingers crossed you can get a few miles on the RD done.


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Kawasaki Z900 A4 , 1976
Yamaha R6, 1999
Yamaha RD 250 D, 1977
Raleigh Chopper Mk2 , 1976

Offline betty foRD

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #24 on: May 14, 2022, 05:22:15 PM »
I don’t think Jools is there yet, but the cap is one more possibility ruled out..


Rev 'em till they rattle

Offline joolsuk

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #25 on: May 15, 2022, 07:51:12 PM »
I just know you are right ...... but hold
my breath on each trip out on bike.
(fuel cap AND both inline filters off
and new petrol lines fitted)

(original issue : running along fine and suddenly
bogs down similar to running out of petrol or
like losing a spark plug and after a few seconds both.
on leaving for 2 mins it works fine again(

I gota add though! Riding the RD on a warm spring
day out in the country puts a smile on your face !
I am 17 again on the very same bike I had back then.

will update post to a finish .
1977 RD250D (mechanical restore)
1980 GS550E
1982 GPZ750R1 (Restore)
1980 GSX250E (mechanical restore)
2002 Stihl FS55 Strimmer (mechanical restore)

Offline AndyDean42

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #26 on: May 17, 2022, 07:02:17 PM »
Check your balance pipe is clear, I recently had my tank professionally painted and during painting I can only assume during the baking one of the exists got blocked by some dirt. I tried clearing with a wire but in the end had to blow it clear using high pressure air. My 350 was bogging down and would not rev freely above 4000 rpm under load. On draining the tank I thought the tap filter was blocked as it was only a dribble on reserve. I tried everything clean carbs improving connections , checked timing, cap vent etc.

Andy
RD400C, RD350B (new project), GS750E

Offline robrd

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #27 on: May 18, 2022, 11:06:02 AM »
What I use to clear the balance pipes is I cut a 3" length of bicycle inner brake cable and use this in a drill to clear them out, the flex allows it to go round the bend but it's not hard enough to do damage.

Offline AndyDean42

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #28 on: May 18, 2022, 07:29:52 PM »
Good idea, I will try some old throttle cable similar to what you use.

Andy
RD400C, RD350B (new project), GS750E

Offline robrd

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Re: RD250D bogging downon runs - must be fuel ?
« Reply #29 on: May 18, 2022, 07:41:38 PM »
Would it be possible that when the bike starts to bog down to turn off the petrol tap and stop the motor, then check how much fuel is in the carbs, if there is little to none, then the fuel feed is the problem, sticky needle valve, petrol tap, float height etc. If carbs are full, it is something in the carb, jets etc.