The CRF305L owners thread

[michael.kozera]

https://www.thumpertalk.com/topic/1120948-crf250l-engine-option/

[yellowrubicon]

I am following this thread closely as I am a big guy (210 lbs) on a small bike and need more power to keep up on the highway and on long grades up hills.  Some interesting diagnostics are listed here: http://www.ultralightnews.com/hirth/readingpistons.htm

regarding piston symptoms and causes.  Seems like exhaust side scuffing is caused by improper lubrication.  What oil is everyone using when they suffered scuffing on their pistons?

[michael.kozera]

I am following this thread closely as I am a big guy (210 lbs) on a small bike and need more power to keep up on the highway and on long grades up hills.  Some interesting diagnostics are listed here: http://www.ultralightnews.com/hirth/readingpistons.htm

regarding piston symptoms and causes.  Seems like exhaust side scuffing is caused by improper lubrication.  What oil is everyone using when they suffered scuffing on their pistons?

 

now-a-days i never use anything less then full synthetic. there is no reason whats so ever to use regular/semi-synthetic oil. (the only time i would use regular oil is for engine break in)

 

not only does full synthetic last longer,(manual says 16,000km oil change interval, full synthetic says 22,000km) but full synthetic lubricates so much better and is far more resistant to oil break down.

same for my car, oil change interval is 20,000km, but with full synthetic it says i can go 32,000km/or 1 year of course.

Edited January 31, 2015 by michael.kozera

[Positron007]

I am following this thread closely as I am a big guy (210 lbs) on a small bike and need more power to keep up on the highway and on long grades up hills.  Some interesting diagnostics are listed here: http://www.ultralightnews.com/hirth/readingpistons.htm

regarding piston symptoms and causes.  Seems like exhaust side scuffing is caused by improper lubrication.  What oil is everyone using when they suffered scuffing on their pistons?

 

I always use synthetic.

[Dirt_699]

Hey guys,

Sorry to bring this back from the dead, not sure why it died in the first place either...

It seems like the discussion about rotating assembly weight was getting somewhere then it just kinda disappeared. Did I miss another thread or something??

I have built many engines and realize the importance of balance when it comes to rotating mass. I think this is a major issue with the 305 kit and should be addressed.

I am going to install a BB kit sometime this year and simply will not put an unbalanced assembly in my engine. Any more progress on this guys? Did anyone weigh the take 305 kit to see if it is closer to stock weight?

Thanks,

Dirt

[Samtech79]

I balanced my crank when I built my 350. The 305 kit piston is pretty hefty compaired to the 250 piston. I'd have to go dig up my notes but I recall it was around 37'ish grams... More than enough to be a problem.

I'm with you, I wouldn't dare do it without balancing the crank to match. There's been a handful of rod failures and to me it points to the lack of balancing and a not so super rod.

My 350 has run with no issues and stock vibration levels longer than some 305 kits have and I attribute this with being properly balanced.

[hockeyrick]

now-a-days i never use anything less then full synthetic. there is no reason whats so ever to use regular/semi-synthetic oil. (the only time i would use regular oil is for engine break in)

 

not only does full synthetic last longer,(manual says 16,000km oil change interval, full synthetic says 22,000km) but full synthetic lubricates so much better and is far more resistant to oil break down.

same for my car, oil change interval is 20,000km, but with full synthetic it says i can go 32,000km/or 1 year of course.

 

I'm with you Mike. Long time supporter of synth! I just change my filter more often (only about $4 here!) to keep the oil cleaner. Even saw a few utube vids on cleaning my old oil(think its a responsible/environmental thing to do)

And with synth, as long as its clean it still is ok, never breaks down!

 

Just saying, gotta do our part and still have high quality lubrication!

[Dirt_699]

I balanced my crank when I built my 350. The 305 kit piston is pretty hefty compaired to the 250 piston. I'd have to go dig up my notes but I recall it was around 37'ish grams... More than enough to be a problem.

I'm with you, I wouldn't dare do it without balancing the crank to match. There's been a handful of rod failures and to me it points to the lack of balancing and a not so super rod.

My 350 has run with no issues and stock vibration levels longer than some 305 kits have and I attribute this with being properly balanced.

thanks for the reply, Samtech,

 

I will split the case if it is necessary to achieve balance, although I would rather try to lighten up the 305 components before resorting to splitting her apart. Such as lighter weight pin and possibly piston.

 

I am glad to see you took the time to do it right and I'm sure you will be rewarded with many years/miles of smooth operation! what crankshaft did you use to achieve 350cc? do you have a build thread???   how many miles do you have on the 350?

 

sorry for the questions I am excited to know that a 350 is achievable on these bikes! also any word on an aftermarket rod for these bikes yet? I would pay almost anything for that piece of mind.

 

Dirt

[Samtech79]

Look in the 349 thread. Lots of info.

The 349...350 is still uncharted water as I think I may have the only running engine so far and it took a lot of work. Fueling problems, clutch problems, wheelie problems, etc.

I've got a bit over 1200 miles of beating the absolute shit out of it so far. After this summers TAT trip I'll tear it down and measure everything.

I will at some point publish a free for all how too cookbook with all the info and fuel maps in one place but I'm keeping in under my hat for now as I can't say for certian that it is a viable long life engine combination.

I will tell you that unfortunately you are stuck splitting the case and weighting the crank. There's not enough meat to trimmed from the piston, pin or rod to compensate for the imbalance.

You don't have to mess with the balancer as its a harmonic balancer but the crank cheeks are gonna need about 50 grams (depending on how far out from center) to bring it in balance with the hefty Wisco piston.

If your set up to do that sort of work you can save a bundle but if not Falicon can do it with a pretty good turn around... But their not cheap.

[Dirt_699]

Nice work! Glad to see someone spearheading this kind of work! I will probably have to outsource the crank welding. Jus curious, has bill blue acknowledged this as an issue? Or takegawa for that matter.

I have been doing research on head porting and I think I will port and polish myself. Thinking of building/buying a flow bench to help with the process. Wish I had a dyno at my disposal!

[Samtech79]

You don't need to weld on the crank. You drill and stuff it with tungsten.

[adamt]

Samtech79, that kind of answered my question. When balancing one of these, are you adding the proportional weight of the piston to the crankshaft counter weight?

[Samtech79]

Well... No, not really. There's a bit more to it.

The distance from the center line plays into it as well.

Also, you can't totally balance a single to cancel out all the felt vibration but you can move the rpm range of where the vibration becomes noticable.

There's a number of papers and books on this which is a bit more than I want to sit here and bang out on an IPhone....

I'll see if I can find one and post a link. It's really pretty simple but you will have to make some precise measurements, do a couple of equations and stick to the rule, measure twice, cut once...

[Samtech79]

Here's a pretty good discription. Easy to understand without too much braining.

http://www.tonyfoale.com/Articles/EngineBalance/EngineBalance.pdf

And here's a video if you really want to hurt your grey matter.

https://m.youtube.com/watch?v=O1xeoRTIAkU

[USMCVietVet]

Well... No, not really. There's a bit more to it.

The distance from the center line plays into it as well.

Also, you can't totally balance a single to cancel out all the felt vibration but you can move the rpm range of where the vibration becomes noticable.

There's a number of papers and books on this which is a bit more than I want to sit here and bang out on an IPhone....

I'll see if I can find one and post a link. It's really pretty simple but you will have to make some precise measurements, do a couple of equations and stick to the rule, measure twice, cut once...

 

Sam is this where we FINELY get to use the algebra they crammed down our neck??? ?

[Dirt_699]

Okay.

Just got an email back from Carrillo regarding a stronger, lighter rod option for our engines. For a 10 rod production run he can produce 60gram lighter carburized version of our rods! At a price of $378ea.

Now this is for a CBR250R rod. Sam, can you confirm these are the same as our rods?

Another question would be is this light enough to make up for a ~50g difference at the piston/pin?

Let me know what you guys think. The production will take 12weeks. I am thinking about going this route regardless for piece of mind.

Let me know how much interest there is in a group buy.

Dirt

[Samtech79]

Yeah it's the same rod as the 250L. You'll still be balancing the crank, maybe not adding weight but making component changes of the rotation assemble is gonna change the balance requirements. You could probably wing it but I wouldnt. Spendy rod... There was some talk about a DLC titanium wrist pin awhile back. Also pretty pricey but ultimately wouldn't help enough to get out of balancing.

[Dirt_699]

Yeah it's the same rod as the 250L. You'll still be balancing the crank, maybe not adding weight but making component changes of the rotation assemble is gonna change the balance requirements. You could probably wing it but I wouldnt. Spendy rod... There was some talk about a DLC titanium wrist pin awhile back. Also pretty pricey but ultimately wouldn't help enough to get out of balancing.

I think I will purchase a rod, regardless of weather I get anyone else on the bandwagon. The reports from the cbr250 forums and this one about rod failure are enough to make it worth it for me. I will then send it out to falicon to have it balanced and see how much of an impact the rod had on the balance. If it gets it close enough (+/- 5g) I would be a happy camper. But I understand it could have a very different effect because of the complexity of single cylinder engine balance. Which is why I will chose to have falicon balance the rotating assembly. With this setup I am hoping for reliable long lasting power! Which is why I'm willing to sink the cash into it now.

Dirt

[Dirt_699]

Ok, so there was some confusion about the weight of the carburized rod vs the stock rod. Sam, any chance you have a stock rod laying around? I need an exact weight please. If not I will wait until I tear mine down.

[Samtech79]

Well... I did at some point but I'm pretty sure it got recycled. I'm also traveling for the next few weeks so I can't go dig through my notebooks and find the wieght.

Might just call Falicon as they make really good quality rods too. Possibly cheaper as well.