Vintage Dirt Bike Q & A

My CR was running ok but it start to have a bit of oil driping at the front of the exhaust. At first I tought it was the oil from the gas. But the last time I ride it, it stoped and never start again. I check the plug and I have good spark, it smell gas but the plug was kind of oily and black. I saw again black oil driping from the exhaust. I removed the head, and it's really oily in the cylinder and on the piston.



I checked the engine oil and it is really low.

I think that the crankshaft seal are maybe damaged and engine oil is going in the cylinder.

What do you think?

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

I concur. Does the gearbox oil smell like gas?

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

The gearbox smell a little bit but not much. But the oil level is really low, it's like the oil is going to the crank compartment, but the gas stay at the top of the combustion chamber.

Ray, do you think I can replace the seal with the engine in place? It's probably only the seal on the clutch side. There's no oil on the other side.

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

No, in this motor the seal can't be replaced with the engine in place - the cases must be split. I did this last year, it's a big job if you replace the bearings etc. (which I did) but not so bad if you just replace the seal. If the motor has a lot of hours on it and you want to keep it, you might as well rebuild it while you have it apart.

It's also possible the leak is at the center case gasket.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

The engine have been rebuild last year I it does not have more than 2 hours of running. I put new bearings, seals, piston, rings, everything. The only thing I can see is a bad seal or I damaged the seal when I installed it.

I don't remember but the seal is not jut behind the primary drive gear on the clutch side? From the owners manual, it look like the seal is behind the bearing, inside the case, is that it? It kind of weird!

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

Oh, OK - then you won't have as much to do. The seal is on the inside of the right main bearing, next to the crankshaft (Honda P/N 91203-360-000 or -003). Honda put the seal there so the right main bearing - and the seal - could be lubricated with gearbox oil. These seals often snag on the right crankwheel 'shoulder' during assembly, and the inner seal lip folds under itself - then when the motor is started, the seal destroys itself in a very short time.

I greased my seal lips and the crank shoulder area, installed it on the crank several times, then left it on the crank overnight before case assembly. The crank went right in, and the motor has a few hours on it now with no problems.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Thanks Ray, I'll try to find the time in the next week. Anyway, the next event I need the Elsinore is at the begining of August. So I have plenty of time to do the job.

Thanks again Ray for your valuable advice!

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

I opened the engine today.

There was plenty of motor oil in the crankcase and on the crank



Sorry for the bad picture


But the seal doesn't look damaged


The gasket also look good


How do I know if the seal is sitting at the right place. Is it back deep enough in it's place? Do I need to push it further?

Do I need to replace it if nothing look bad?


This seal is new from last year. I don't know if I really need to replace it or if I just put it back with some grease like you wrote in a previous reply. What do you think Ray?

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

That's not the correct seal. The OEM 91203-360-003 is a 28x56x9mm double-lip seal, probably rated for at least 10,000 rpm sustained operation. The one you have appears to be a 28x56x8 single-lip seal, and the lip looks very thin to me. Where did you get these from?

I'd highly recommend using the Honda seal in this very critical location. The inner (crank side) lip is very wide with what looks like some kind of (break-in?) coating, each lip has its own circular tensioning spring, the gearbox side has small stand-offs to allow oil inside the seal and bearing, etc.

There's quite a few of these on eBay right now, and CMSNL has them too.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Ray, you have eyes of a lynx!!!

You are right. I checked on CMSNL parts list, and the seal must be 28x56x9mm double lips and I have a 28x56x8mm single lips.

I bought a complete seal kit from BossBearing. On my bill, the item number is 330607984033. This number is not available anymore on Bossbearing website. I bought that on November 2012. They probably found their mistake and replaced it with this kit: http://www.bossbearing.com/Engine-Oil-Seals-Kit-p/db-967.htm They indicated that all seals are double lips.

They got me on this one!

I checked the seal on the rotor side, and this one is a double lips and it doesn't leak.

I'll replace it with a good one, thanks again!!!

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

these kits are not good, all seals are std-parts.
double lips there means one seallip and one dustlip. but you need double seallip.
for the crank use only original honda seals on both sides.

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80 CR250Ra
80 CR250Ra
78 CR250R
80 CR80
82 Bultaco Sherpa 340
78 Bultaco Pursang 250 MK12
76 Bultaco Frontera 370 MK10
76 Bultaco Alpina 250
73 Bultaco Lobito 125 MK6
76 Suzuki RM125A
90 Kawasaki KX250

I received the seal today, it look a lot more strong than the one I have in the engine right now.

I'll use the method Ray wrote earlier a few post above.

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

Bad news.... I 've just put a Bossbearing kit on my 76 250..... I'm going to check if this problem occurs to my engine...

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1976 CR250M - 1975 KAWASAKI 900Z1 - 2012 KTM 450 EXCF - 1965 GT mustang (conv) - 1944 Willys MB jeep

Maybe they upgraded their kit... I wish it for you!

My engine is rebuilt but I didn't have the time to try it. I'll give a try in the next 2 weeks.

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1974 Honda CR125M - 1977 Honda CB750 - 1982 Yamaha XT550 - 1986 Honda TLR200 - 2016 Honda CRF1000L Africa Twin- 2012 Ossa TR280i

Hopefully that was readable I was trying to do talk to text to my phone and sometimes it spazzes a little bit maybe you got the message anyways thery're in town where you li there in town where you live you just have to dig around a little bit and find them and wherever you find them you can find any future seals you may need