Kr 250 A Blowing smoke using gear box oil quick

The place to talk about your Tandem!
TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Mon Jul 09, 2018 12:12 pm

Thanks, That's a good idea. I was thinking of machining down the circlip lands and pressing on a sleeve but that's a better Idea. I will heat the shaft with the oxy and then use the Mig to tack some lands back on. Sounds like a plan.
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Tue Jul 10, 2018 11:05 am

I went to my local welding and gas cutting supplier today and took the shaft. We had a bit of a chat about the best way to repair the shaft with the tools and equipment that I had available. we decided to use the Oxy-acetylene welder using a slightly oxidising flame and NBF rods (Nickel Bronze Filler) according to the manufactures recommendations NBF is used to repair gears and shafts and is extremely hard wearing. So I have now repaired the shaft and it looks pretty good to me. Went and got new bearings and seals as well, so I will now start to clean parts properly for re assembling.

I asked this question a couple of posts back but don't think I got an answer, see question below.

I found the primary gear seals in the rotor/reed valve assembly installed one way in one motor and reversed in the other. What is the correct way? It's hard to tell from the PDF manual.
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

User avatar
JanBros
Premix Junkie
Posts: 2987
Joined: Wed Jul 26, 2006 11:50 pm
Location: the land of Francorchamps
Contact:

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by JanBros » Tue Jul 10, 2018 11:58 am

you always have a circular spring on one side : that side must go to the side with the highest preasue. the spring delivers a primary pression on the seal, the higher the preasure behind the seal the better the sealing because the higher preaure pushes extra on the seal.

so in your case : to the crankcase-side.
You know it's cold outside when you trip over dog shit instead of standing in it.

TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Wed Jul 11, 2018 12:45 pm

Correct But these engines do end up sucking the oil from the gear box in to the crankcase. The pressure fluctuates and become a negative pressure/vacuum to draw the air and fuel in to the engine. I think this is why they do end up sucking the gear box oil into the engine. So someone has reversed the seals in one engine to overcome this issue. I wonder how well this actually worked. I will put my seals in with the spring on the crankcase side as you have specified the manufacture did it as they should know best.
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

User avatar
StrokerBoy
Premix Junkie
Posts: 1021
Joined: Thu Jul 27, 2006 9:43 am
Location: Yorkshire
Contact:

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by StrokerBoy » Wed Jul 11, 2018 4:48 pm

TurboStew wrote:
Wed Jul 11, 2018 12:45 pm
the manufacture did it as they should know best.
The manufacturer who binned the tandem-twin after a couple of years and reverted to a much simpler parallel-twin design... :mrgreen: :lol:
Kawasaki KR250 Tandem Twin (x4) & KS-II 80,
Yamaha RD350LC,
Suzuki GSX-R750RK & RB50 Gag.

User avatar
JanBros
Premix Junkie
Posts: 2987
Joined: Wed Jul 26, 2006 11:50 pm
Location: the land of Francorchamps
Contact:

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by JanBros » Wed Jul 11, 2018 6:08 pm

TurboStew wrote:
Wed Jul 11, 2018 12:45 pm
But these engines do end up sucking the oil from the gear box in to the crankcase. The pressure fluctuates and become a negative pressure/vacuum to draw the air and fuel in to the engine.
only when the seal is no longer sealing ;-)
You know it's cold outside when you trip over dog shit instead of standing in it.

TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Thu Jul 12, 2018 1:20 pm

Went out to my garage today to put the motor back together, but I couldn't bring my self to do it because the paint on the cases was faded, peeling and scratched. I stripped all the paint off and masked them up and re-painted them. They look good now.


Some pictures:

Repaired shaft:
http://rs1313.pbsrc.com/albums/t542/bon ... n.jpg~c100

Paint stripped:
http://rs1313.pbsrc.com/albums/t542/bon ... a.jpg~c100

Ready to paint:
http://rs1313.pbsrc.com/albums/t542/bon ... b.jpg~c100
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Fri Jul 13, 2018 1:35 pm

Yet another day with nothing to show on this bike, talk about one step forward, 10 steps back. Started to put the motor together with all new bearings and seals. the old motor had a lot of bearing play on the water pump side in both crankshafts. The bearings just fall off the LHS of the crank shaft so I ended up using the cranks out of the other motor I got. Putting it back together I still had a lot of play in the LHS cranks. Dam it the casings are shot as well. So I spent the rest of the day cleaning, removing paint on the second set of casings and got them painted. Will have another go at it tomorrow. Hope I have a better day and have something to show for my efforts.
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Sat Jul 14, 2018 10:15 am

Hi, I'm Just wondering if anyone else has had this happen to their engine casings? On the engine I was rebuilding, both the LHS front and rear crankshaft cones that are factory fitted into the aluminium casings have both hammed out in the casing. They will not come out even though they are loose. The crankshaft bearings press into these shells and they are obviously a reinforcement to aluminium case to make the bottom end stronger.
Yeah that didn't work.
So who else has had this happen to their engine?
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

Gerrit
Heavy Smoker
Posts: 271
Joined: Fri Jun 26, 2009 12:09 am
Location: Kingdom of the Netherlands

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by Gerrit » Sat Jul 14, 2018 11:57 am

Not sure if I understand you correctly, but I presume you are referring to the bores for the LH crankshaft main bearings. They are probably steel inserts around which the cases are cast. On H1s and H2s (which have horizontally split cases) they are secured by dovetails on the OD of the steel shells and I assume that KHI used the same system or something similar on the tandem twins. if these steel inserts are loose the dovetails wil prevent their removal. The only solution, apart from new cases, is having a competent engineering firm machining them out and inserting new steel inserts. The bores will have to be in alignment with the RH bores, I'd have the interference fit of the RH main bearings checked at the same time as the LH bores are dealt with. No quick fix here, I'm afraid.
"Mine is a long and sad tale", said the mouse.
"Indeed it is", said Alice, looking at the mouse's tail.

TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Sat Jul 14, 2018 12:38 pm

Thanks Gerrit, your 100% correct in my description and your interpretation of my post. Yeah I figured not a simple fix and figured the case will have to be machines and new steel shells fitted for the bearings and yes they are held in with some sort of dovetail. Lucky I had another 1/2 decent set. So do you know if this is a common failure of these engines?
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

Gerrit
Heavy Smoker
Posts: 271
Joined: Fri Jun 26, 2009 12:09 am
Location: Kingdom of the Netherlands

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by Gerrit » Sat Jul 14, 2018 2:34 pm

I'm afraid I can't answer that- I don't have a tandem twin as they were never sold in Holland or most other countries in Europe with the exception of some grey imports in (then West) Germany and the UK. Two sets of cases with the same fault suggests it may be a fairly common occurrence however, ditto for the failure of the gearbox shaft you described. I suspect the faults only show up on engines that are used hard (especially if poorly maintained), and that those that have been used moderately may be free of these defects.
"Mine is a long and sad tale", said the mouse.
"Indeed it is", said Alice, looking at the mouse's tail.

Gerrit
Heavy Smoker
Posts: 271
Joined: Fri Jun 26, 2009 12:09 am
Location: Kingdom of the Netherlands

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by Gerrit » Thu Jul 19, 2018 11:30 am

It's always interesting to discover why a part fails, e.g the gearbox shaft. According to the service manuals the input shaft's second gear is fixed by the splines on the shaft, next to it is 5th gear which is free to rotate when not engaged. 5th gear is engaged when the combined 3rd/4th gear slides to the left causing the dogs on both gears to engage. However, when the dogs don't engage as they should immediately but first jam against each other axially, the force is transmitted through 5th and 2nd gears to the circlip and thus to the part of the splines to the left of the circlip groove. If this occurs repeatedly the ends of the splines will eventually fail as they are rather thin. This probably only occurs when an engine is used hard i.e. racing or spirited street riding, though.
"Mine is a long and sad tale", said the mouse.
"Indeed it is", said Alice, looking at the mouse's tail.

TurboStew
Light Smoker
Posts: 45
Joined: Sat Jan 10, 2015 2:06 pm
Location: Melbourne Au

Re: Kr 250 A Blowing smoke using gear box oil quick

Post by TurboStew » Sat Jul 21, 2018 2:35 pm

Gerrit wrote:
Thu Jul 19, 2018 11:30 am
It's always interesting to discover why a part fails, e.g the gearbox shaft. According to the service manuals the input shaft's second gear is fixed by the splines on the shaft, next to it is 5th gear which is free to rotate when not engaged. 5th gear is engaged when the combined 3rd/4th gear slides to the left causing the dogs on both gears to engage. However, when the dogs don't engage as they should immediately but first jam against each other axially, the force is transmitted through 5th and 2nd gears to the circlip and thus to the part of the splines to the left of the circlip groove. If this occurs repeatedly the ends of the splines will eventually fail as they are rather thin. This probably only occurs when an engine is used hard i.e. racing or spirited street riding, though.
Yeah Gerrit, I figured some sort of side thrust would have been the cause of the failure. I was thinking along your line of thought. Finally put the engine back in the bike today and got it fired up, Well after I sorted a few other issues that always crop up when your dealing with old bikes. Got a little frustrating at one stage :evil: . Yeah no smoke or oil coming out the exhaust. 8) However one carburettor is flooding so I will have to reset the float level.
(2x) GPZ 750 Turbo, E1 1984 & E2 1985
KDX 175 B2
1997 GSXR 750 SRAD Blue/White
1984 KR 250 A Tandem Twin, Green
1985 KR 250 A2 Tandem Twin, Red

Post Reply

Who is online

Users browsing this forum: No registered users and 7 guests