facts on the new CRF250f

[mixxer]

17 minutes ago, highmarker said:

I said stock vs stock because I knew there would someone with a mod 230 jump in and compare to a stock 250.  IMO it's crazy to put used real-bbike money into any of these price point parts bin entry level bikes.  But we love our hobby's and there is satisfaction of making something work better.   Stock just bigger forks and increased wheel base is an improvement, rear disc long overdue.  Is it worth the added weight? hard to say till riding one.  Know guys that still prefer the 200, think the 230 is a porker.

Ahhhhhhhhhh....

But mine has killer XR suspension

... Very very fast....

Love my little red piggy...

200 is missing magic button...

Tit for tat...

Edited November 17, 2018 by mixxer

[SmokinJoe]

I wonder if there will be a aftermarket plastic fuel tank option since the oem one is steel it has to be adding weight. 

[SteveThe Snakes]

We don’t yet know the future of the new 250. At least it isn’t a L or it would be a real overweight piggy. It likely has a monster heavy crank and possibly is more of a stroker than a bigger bore high rpm type engine. That leaves itself toward us type of people. Time will tell what happens with the aftermarket. 

[mixxer]

5 hours ago, MetricMuscle said:

Might you know if this engine can be stroked more than 4mm without major mods?  Is the 2mm stepped pin a straight forward install, no relieving of shafts or the case?

I am always more concerned with volumetric efficiency of the engine..   flow and feed... Since , when done right, that will make for solid, if not massive gains... Camshafts / Porting/ Carbs (throttle bodies)/ Intakes / Valves / Pipes/ orrect jetting (mapping)... Compression and combustion chamber shape & critical dimensions..

That's my list of what comes first... High VE in the area I want the engine to work in...

Then I will consider about making it bigger displacement....

All too often people are confusing the simple statement/philosophy that "bigger" is instantly and inherently "better" ... And it most certainly is not!!..

You go bigger without nailing down your flow and feed of this air pump.... And congratulations, you have now taken inefficient... And made it even more inefficient at feeding a bigger displacement...

If it sucks at feeding 250cc...  Why would I want to have it suck worse feeding 300??

Displacement is only fine if it's fed.... So ... Nice... But last on my list...

Also... If possible... I prefer bore kits to stroker cranks if I had to pick only one way to increase displacement... But that's a whole 'nother topic...

[xjnewfie]

I personally am very excited to see some real world testing of this bike. I've fallen in love with my 230 after years of riding the big boy bikes, but would love it if it had a few more CCs, HP, Fuel Injection, a rear disk brake... I suspect this new 250 will be a much better bike once the aftermarket jumps on board with support. I guess time will tell.

[bajatrailrider]

This bike was old news lacking before its for sale. 

[woodsryder]

I lost all interest after learning the weight. someone said actual weight 289lbs!!!!!!!!!!!  Thats over 100 lbs heavier than my ultralight BBR/CRF/XR Frankenstien bike.

Then I thought maybe the motor has some potential in a lighter chassis,... Nope!  Its still an 85 lb boat anchor and 450 motors with twice the power weigh 20 lbs less

Over complicated, grossly overweight, poor suspension, overstyled,... typical modern bike. It is what it is,... buy it and ride it if that's all you need out of a bike and many people don't need more. Its just not a good starting point for any kind of performance oriented machine. 

Most every bike I own is modified beyond recognition but I do have a bone stock DR650 which fits in the same category, its a lost cause trying to improve it but its still a likable reliable air cooled pig that makes you smile.  

[adnohguy]

But can the 4 valve cylinder and head be grafted to a 230f engine?

 

Greenhuman may have a clue?

[RND.23]

2 horas atrás, adnohguy disse:

Mas o cilindro e a cabeça de 4 válvulas podem ser enxertados em um motor 230f?

Unfortunately not.

The cam chain is in the right side of the engine, and, unless you cut the chassis, the header pipe will not fit.

[woodsryder]

Pftt,... Greenhuman could weld that up and move it to the other side before lunch. ? 

Too bad, otherwise it looks like a nice set of parts. I like the substantial fins on the head compared to ours.

Seriously I looked at the DR350 and XR350 top ends and they have the same issue. 

Edited November 21, 2018 by woodsryder

[adnohguy]

Unfortunately not. The cam chain is in the right side of the engine, and, unless you cut the chassis, the header pipe will not fit.

 

 

 Oh, Darn [emoji1304][emoji53]

 

But does it have a 3 piece metal head gasket that can be separated to use just one layer?

Then clean up the ports as required, build an oversized header (utilizing the stock muffler) and build an advanced key to give it a few extra degrees of advanced ignition timing.

Degree the cam to find out where it is stock and then advance it a few degrees for a smidge more lower rpm pull.

It all adds up until the aftermarket comes us with ECM tuners, cam shafts, exhaust systems, big bore piston kits, etc.

 

Or even:

 For $300.00

One could have Crank Works stroke the crank 4mm with a stock length OEM connecting rod then the when adding an extra base gasket to advance the stock cam timing slightly, whittle on the stock piston in the lathe to get the squish clearance at the optimum bare minimum for more cc with even more compression.

 

71x67 = 265cc

 

 

[The Plvis]

17 minutes ago, adnohguy said:

 

Oh, Darn

 

The more I look at this new creature, the more i see its junk. Its a newbies bike or someone that doesn't know better. The 150F is the purist platform. Has anyone thought of strength welding the case where the 150F kick starter breaks?

I'm starting to get sick looking at Honda new 250F creature!  

[RND.23]

The power curve seems to be very similar to a 2 valves engine, but it has more power through the whole rpm range.  

[JRM]

This "new" engine looks a lot like the first generation XR250 engine that Honda used in 1978-1982 prior to the RFVC! Both are a pent roof 4 valve SOHC with right side cam chain- both even have the same rubber cam plug and a 5 speed engine! bottom end is totally redesigned but that top end looks awfully close to this>

https://www.motorcyclespecs.co.za/model/Honda/honda_xr250r 79.htm

 

Edited November 22, 2018 by JRM

[RND.23]

9 hours ago, JRM said:

This "new" engine looks a lot like the first generation XR250 engine that Honda used in 1978-1982 prior to the RFVC! Both are a pent roof 4 valve SOHC with right side cam chain- both even have the same rubber cam plug and a 5 speed engine! bottom end is totally redesigned but that top end looks awfully close to this>

https://www.motorcyclespecs.co.za/model/Honda/honda_xr250r 79.htm

 

Very interesting, but it has nothing to do with the RFVC of the XR's... 

The CRF head is SOHC four valves, pent roof chamber.

The XR head is RFVC (radial four valves...) with a hemispheric chamber.

In the CRF, we have a single cam with two lobes, and roller rocker arms.

In the XR, we have a single cam too, but it has four lobes and a very complicated system of arms to make the parallel movement into radial.

In the CRF, the spark plug comes from the left side of the head. 

In the XR, the spark plug comes from the front side.

[JRM]

Exactly, its very close to the 1978-82 xr250 prior to the RFVC radial head that uses sub rocker arms used from 83-04 here is the left side of that 1978 engine im talking about- the 2019 is indeed slimmed down, but the basic design is strait up out of the history books! 

Edited November 23, 2018 by JRM

[YZEtc]

How are the valve clearances adjusted on the new CRF250F?

[adnohguy]

How are the valve clearances adjusted on the new CRF250F?

Looking at the photo above they appear to be adjusted by an eccentric rocker shaft possibly?
But I certainly don’t like the appearance of no way to adjust each valve individually unless grinding on the valve stem [emoji15]

Ridiculous if that really is the case?

[JRM]

I don't think that 1978 had roller rockers that part I'm sure has been completely redesigned

Sent from my LG-H871 using ThumperTalk mobile app

[Doogee57]

On ‎11‎/‎23‎/‎2018 at 9:52 AM, adnohguy said:

Looking at the photo above they appear to be adjusted by an eccentric rocker shaft possibly?
But I certainly don’t like the appearance of no way to adjust each valve individually unless grinding on the valve stem

   Looks like there's a shim in the retainer's pocket ala CRF250R/X. A good way to do it.