Valve Seal Replacement - K-Bikes.com - Excellence in Motion
 
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post #1 of 8 (permalink) Old Jan 26th, 2020, 11:03 am Thread Starter
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Valve Seal Replacement

Hello,
I have a 98 K1200RS Taxi which is very well cared for. My question to the group is at what point do you consider replacement of the valve seals due to the combination of age and miles?

The bike runs very well with some oil consumption of about 1/2 quart every 1500 miles. This does not bother me, though I do wonder if I could reduce this if I replaced the valve seals. My theory is that the seals are so old now that they have lost their flexibility.

thanks, Joe
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post #2 of 8 (permalink) Old Jan 26th, 2020, 3:25 pm
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Find a riding partner.Crank her up into the the high rpms and then downshift keeping revs up there.5-6000 rpms will do.6000 is? 100mph!

Ask the partner if he sees smoke coming out of the exhaust under hard compression braking? If it smokes then that is more than likely valve seals and/or worn guides.

My 03 smokes a little under hard acceleration or so said my nephew.Has more to do with the quick richening of the fuel/air mix than burning oil altough mine is at 1L/10,000 kms at now 293,000 kms.Them good green umbrella shaped valve seals will outlast my bike....!

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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post #3 of 8 (permalink) Old Jan 27th, 2020, 12:11 am Thread Starter
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Thanks for the comment. I will try to do the check.
Tried a leak down test but had difficulty keeping the crank from turning once I turned the air on. There was just too much pressure in the cylinder to listen for where air was escaping. And I could not get the crank at absolute TDC for some reason even with putting the tranny in 3rd for 4th gear.
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post #4 of 8 (permalink) Old Jan 27th, 2020, 3:57 pm
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My 98 KRS is burning 1/2 quart every 600 miles now with 57k on the odo. It runs plenty strong, as strong as my 2000 with 17k miles and with similar compression readings. Worn valve guides are therefore the diagnosis for my 98.
At your oil consumption Id run her as is.

98 K12RS taxi, 2000 K12RS taxi, 2004 K12GT, 2009 GSA, 2014 R-Nine-T
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post #5 of 8 (permalink) Old Jan 27th, 2020, 5:20 pm
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I was reading something recently about the 98s and their propensity to seize up at No1 conrod.

Apparently BMW then undersized the crank journals lube holes.Crank of course is first to be lubed on the Ks oiling plan but smaller passages could restrict oil flow to piston skirts/oil rings etc....!

Anyway I personally know 3 riders who seized up/broke conrods on 98s.

So in 99 BMW addressed that and conrods changed from conventional to the cold fractured/fracture-split type and apparently then increased the oil delivery via larger holes.

Apparently larger holes....I can't confirm that!

Interesting that Clymer is showing an early motor disassembly! Did they miss that update?

https://mitchell1.com/shopconnection...a-broken-part/

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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post #6 of 8 (permalink) Old Jan 27th, 2020, 5:52 pm Thread Starter
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Thank you for your comment 98Taxi. That is where my head is at. I just wanted to know if anyone had a passionate answer for changing the seals.
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post #7 of 8 (permalink) Old Jan 27th, 2020, 5:55 pm Thread Starter
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So let me ask you a question. Suppose you had a 98 and for some reason had to take off the crank cover. Would/Could you just take off the no. 1 cylinder con rod cap and check it out?

Thanks, Joe
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post #8 of 8 (permalink) Old Jan 27th, 2020, 6:52 pm
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I should have a couple conrod nuts here.t one time I tought the later Ks could also suffer.So somewhat prepared to look at No1 on my 03....bought the nuts and figured out that later engines have different conrod bolts.

But being in my bike for high milleage I installed an oil pressure gauge and have been monitoring that for 10yrs.I never even noticed my defective idiot light last summer,must have been out for a few days.....!

Idiot light spec is 5-8psi.Engine runs at well above that even at idle.

Last blown 98 on here was a few years ago.Owner had previously noticed the oil light not going off quickly at startup as it should.And maybe a little knocking at cold idle but didn't take action.Too late?....conrod broke later on.

Anyway.....as per Clymer conrod bolts/nuts should be replaced as they are the stretch type? Wouldn't cost much but oil pressure gauges also do not cost much.

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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