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headgasket probs.. stock mikuni?

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I have a 05 drz-sm with a stroker/bb i bought with a bad headgasket in the spring i fixed it and rode all summer put about 1600 miles on and i didnt baby it.... i was told by another member of TT when i was in the repair process that " the mikuni with the stroker/bb could cause head gasket failure again and i should switch to the fcr 39 or 41".... i was wondering if any body coiuld help fill me in on why it would fail because of that... thanks

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I can think of no relation between big bore head gasket life and Mikuni carb. If anythig, the increased performance potential of a 39 or 41mm Keihin FCR would be harder on the head gasket than the Mikuni BSR36.

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What kind of cams are in it? The only issue I have read about is if you don't have the right cams with enough overlap your compression pressure with the stroker gets to high enough levels to blow headgskets. I have no personal experience with this but have read this many times on here.

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+1 on what Noble said.

I think head gasket failure has higher rates if bored to (94,5 mm) or more because it's narrower between water jacket port and cylinder wall. (not sure if it is from 94,5 or 95 mm and more)... soooo, is it bored to more than 94 mm? and is the cylinder casting similar to the stock one?(especially in the section between cyl. wall and water jacket)...if too thin, it will fail for sure. Just a matter of time....

The 39/41 mm fcr would allow more a/f mixture so, in theory, more energy and more stress on that cross section of the head gasket from the bigger explosion than with the bsr36.

...

What are your cams + cam specs.

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its a 480 bb/ stroker stock cams..... when i put the new gasket in the head bolts were loose.. im assuming because the spring washers were upside down?

so what i gathered out of this is that if i go with a bigger carb i have to get diff cams to prevent any further dammage? any sugestions? all i have herd of is hotcams...

thanks for the info! :smirk:

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i know the bore is 95.5 mm unsure of stroke.... its a flattop piston with no valve reliefs... i only know its a 480 b/c of the repair shop who installed it

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its a 480 bb/ stroker stock cams..... when i put the new gasket in the head bolts were loose.. im assuming because the spring washers were upside down?

so what i gathered out of this is that if i go with a bigger carb i have to get diff cams to prevent any further dammage? any sugestions? all i have herd of is hotcams...

thanks for the info! :smirk:

There are no spring washers under the head bolts, or should not be.. OEM ones are flat, surface ground hardened washers, and the best of all options available.

Some early BB kits included copper washers,,, and some folks used them before word got around.... Toss them thinks in the trash and reuse the OEM washer.

If you bought a kit that has cupped spring steel washers, please name the kit... And Id suggest not using them, using the OEM style washers,, TQ'ing the head bolts to 43 ft lb.

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i know the bore is 95.5 mm unsure of stroke.... its a flattop piston with no valve reliefs... i only know its a 480 b/c of the repair shop who installed it

With a 95.5 mm bore, you will continue to have head gasket issues as long as your using OEM or Hot cams.. This is seen time and time again.

Quality gasket, good prep, copper coat the gasket, 43 ft lb TQ and you can get by sometimes, but many still have issues with that bore and .. Contact SSW if you want a set of cams that will help with the issue.

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Yes , and even when using the correct cams(something like RHC 187 cams)...You have a better than good chance of head gasket seal issues when venturing bigger than 94mm bore....

I have recently realised this through my own real world experience...resulting in a slide down the road with busted body parts...

Fit a catch can for possible coolant overflow, which can occur from blowing a head gasket....

Do everything right ,as Eric has mentioned, to reduce the likely hood of this occurring...

Edited by craigodrz400sm

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With a 95.5 mm bore, you will continue to have head gasket issues as long as your using OEM or Hot cams.. This is seen time and time again.

Quality gasket, good prep, copper coat the gasket, 43 ft lb TQ and you can get by sometimes, but many still have issues with that bore and .. Contact SSW if you want a set of cams that will help with the issue.

Yes , and even when using the correct cams(something like RHC 187 cams)...You have a better than good chance of head gasket seal issues when venturing bigger than 94mm bore....

I have recently realised this through my own real world experience...resulting in a slide down the road with busted body parts...

Fit a catch can for possible coolant overflow, which can occur from blowing a head gasket....

Do everything right ,as Eric has mentioned, to reduce the likely hood of this occurring...

it semms the cams r the only thing i will be changing plus the carb..... but why r hot cam a bad choice?

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it semms the cams r the only thing i will be changing plus the carb..... but why r hot cam a bad choice?

Not enough duration to deal with the increase combustion area....

Better volumetric efficiency can be achieved with more cam duration...

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Not enough duration to deal with the increase combustion area......

Better volumetric efficiency can be achieved with more cam duration...

ok i get that thanks! i been reading alot about exhausts too.. the bike came witha full fmf powercore four.... from what i gather all this pipe does is make noise with not much power increase is the yoshi that much beter... or could the ppower bomb deliver the profamace i am after?

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ok i get that thanks! i been reading alot about exhausts too.. the bike came witha full fmf powercore four.... from what i gather all this pipe does is make noise with not much power increase is the yoshi that much beter... or could the ppower bomb deliver the profamace i am after?

..

It depends on what power your chasing...

To take your stroker to it's potential your need the correct parts...41mm Fcr , rhc 187 cams, +1mm valves, ssw/mrd pipe

The FMF does not flow as well as an SSW/MRD, so it will restrict your HP potential..

It will still deliver a usable power range but your top end will be lacking..

The engine is like an air pump; the more air that is allowed to flow through it, the more horsepower that you get out of it.

If you have a free-flowing air/fuel intake and exhaust system you’ll get more horsepower because of the efficient flow of air into and out of the engine.

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..

It depends on what power your chasing...

To take your stroker to it's potential your need the correct parts...41mm Fcr , rhc 187 cams, +1mm valves, ssw/mrd pipe

The FMF does not flow as well as an SSW/MRD, so it will restrict your HP potential..

It will still deliver a usable power range but your top end will be lacking..

The engine is like an air pump; the more air that is allowed to flow through it, the more horsepower that you get out of it.

If you have a free-flowing air/fuel intake and exhaust system you’ll get more horsepower because of the efficient flow of air into and out of the engine.

now when u say top end power im assuming that u mean top end in the rpms? and i dont know where to look for the ssw pipes and the cams.....

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