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Hi, new to the forum and new to the CRF150R.

Bought a basket case CRF150R, the two engines where supposed to be from 2007-09.

But when I compare the combustion chambers they are different.

I believe one of the heads are of the later design, but I can't say which.

My problem is to buy the right piston...

I would be grateful for any advice.

Here is a pic of the two heads.

Kind regards Christer / Sweden

After a research on eBay, it seems as the head with the smaller combustion chamber is the older one.
Probably from 2007 - 09.
The head with the more open chamber might be from 2012 and forward.
I also found a old style head that was modified a little lika the new head.

Would still be grateful for more input on the subject.
Whats the gain with the newer design?

I think I will go with the old head since I have ordered a -07 B-piston for it.

HälsC

Hi V150 and welcome to the site,

I think you decision to stay with the more closed chamber is wise since you have the piston.
The other head looks like it may flow more (similar to Tokyo Mods chamber) but you would have to find the matching piston for it to work.

What are the engine numbers the respective heads came off?
This should give an idea of year.

Thanks Aussie,
the engine numbers are 5006994 and 5110582.
What I have found it means a 2007 and a 2008/09 head.

The bike has been on the track for some years, there have probably been many updates.

The strange thing is that the three piston which come along looks almost the same.
Last time it was running was with the newer (more open) head, but the piston looks like the others.

Well, I might understand more when I get the new piston.

Any big changes with the carburetor between 2007 to 2012?

Grateful for any info in the subject.
CheersC

I would think if the depth is the same for the chambers the open chamber would have either a taller piston (above gudgeon pin) or a smaller dish to keep compression ratio the same.

As far as carbys I suggest you look at the parts manual here.
http://partsfinder.onlinemicrofiche.com ... ke=hondadb

That way you can see by part numbers if a change took place.
The jets and needle are a good place to compare.
Other than that internet research, but be careful of wayward claims.

It would appear that a lot of add on bits work for 2007 - 2019.
https://www.crfsonly.com/catalog/index. ... /4a/page/1

Hope that helps.
There maybe more info in the 150R forum on the site.

Thanks Ray,
I got the new piston.
Its a Wiseco, Nr. 4915M06600 for 2007-09.

What happened 2010-2011?
As far as I know the head changed first in 2012.
The mystery goes on

Anyway, the pistons is exactly the same that the one last used in the bike, together with the 2012 head.
So probably it did run with a bit low compression.

Now I have the right piston for the old head, ok for now

There are two carbs with the bike, one with a red R&D float chamber, will start with this one.
Will do the homework that you suggest and check needle and jets.

Any experience with parts like FMF Snap?

I also thinking about a little more weight on the flywheel.

Any more tricks for getting the best out of the engine at low revs?

My son is a beginner, getting the best out of an old XR80 for the moment.
So it will be a big step for him.
Therefore Im interested in getting the 150R more gentle than wild for the moment.
So any tips in that direction are welcomed!

Here in Gothenburg its hot today, +20° for the first time this year

Cheers Christer

Hi Christer,
Is it a big wheel version?

The 150R will definitely be a step up in performance.

If you want smoother low down the extra weight on the flywheel will sort it out.
Even a change form an alloy clutch plates to a steel ones helps, but only if you need to replace them.

Another think you can do to make it mellow is change the gearing.
One tooth up on the front will make it less jerky on the throttle at low speed.

The other thing you might be able to do is find a way to limit throttle travel for the moment till he begs for more go.

Yep its a big wheel.
My son is short for his age, I will make a low-link, push up the fork legs and cut down the seat.
If that's not enough I might make a new lower back-fram, then when his growing we can change back.

I didn't know there was steel plates, good to now. But I got three sets of standard plates...

Will measure the valves and guides on Monday, will probably change the guides.
Will get at more experienced friend opinion.

Still waiting for the new crank and bearings, hope to have it next week.

My son keps training on the old XR80, two days ago the beginners got their first ride on the big track.
I felt sorry for him on the big bumps, but on the steep uphill he could surprisingly just plodder on third gear, many two strokes rider
got engine stops when they climbed on to high gear

How often should I change oil on the CRF150R?
I heard every 5 hours, and every 10 hours also change the filter.
Does that sounds ok?

Cheers Christer

Hi Christer,
Not saying you can get steel clutch plates for that model but is a trick when you can.

The owners manual probably has those times to change oil and clean filters.
This was designed for when the bike is being raced.
If your son is only trail/woods riding you could safely extend those times.
This may change as he learns to ride it faster.
Best way is to inspect often and replace or clean when you notice a change.
Remember though oil is cheaper than an engine and more engines have died because the air cleaner let dirt in to the engine.
Not only must they be oiled just right but seal against the air box.