KLX 250 ( 300 ) camshaft mod by Marcelino
#891
03-15-2016, 04:39 AM
klx678, no one except Jhoffy22 did the complete MCM on a 351. Some others(351'ers) did only the intake cam - reporting good results. IIRC, one 351'er reported worse performance and increased intake growl - meaning he didn't do it right..
We do have posts where Bill was asked if the 351 kit has less valve clearance - the answer being no, the piston to valve clearance remains same-as-stockbore..
If I was Bill Blue and a 351 customer called me up to ask my opinion on his (the customer) fooling with cam phasing, I'd have one answer too - Don't do it!
We do have posts where Bill was asked if the 351 kit has less valve clearance - the answer being no, the piston to valve clearance remains same-as-stockbore..
If I was Bill Blue and a 351 customer called me up to ask my opinion on his (the customer) fooling with cam phasing, I'd have one answer too - Don't do it!
#892
03-15-2016, 05:05 AM
For the record: JHoffy 351 build was faulty from the start, because he did not torque the head bolts when first doing it. This is something I remember very well because it stroke me at that time. There were a few postings on the subject then. He had the head bolts torqued properly after some hours on the 351, but head gaskets are not meant to be reusable and torqueing them anew after some used hours does not necessarily mean it will seal right. Who knows what this can lead to. Exhaust valves sized in their guide due to head deformation is just one possible outcome. Correct me if I'm wrong...
That being said, I am one who believes the MCM makes plenty of sense, based on the physics involved in engine hydrodynamics, particularly the intake process. Closing the intake valve at 52deg ABDC instead of 62deg would keep a greater proportion of the 250cc stroke inside the cylinder for compression, at rpms below intake resonance. But the benefits would be less for a 351 bore, as the relative resistance to flow of the intake valves becomes more important (unless they are made larger).
Take it with a grain of salt, I am no engine expert and I don't have experimental numbers to back up these beliefs.
That being said, I am one who believes the MCM makes plenty of sense, based on the physics involved in engine hydrodynamics, particularly the intake process. Closing the intake valve at 52deg ABDC instead of 62deg would keep a greater proportion of the 250cc stroke inside the cylinder for compression, at rpms below intake resonance. But the benefits would be less for a 351 bore, as the relative resistance to flow of the intake valves becomes more important (unless they are made larger).
Take it with a grain of salt, I am no engine expert and I don't have experimental numbers to back up these beliefs.
#893
03-15-2016, 12:28 PM
For the record: JHoffy 351 build was faulty from the start, because he did not torque the head bolts when first doing it. This is something I remember very well because it stroke me at that time. There were a few postings on the subject then. He had the head bolts torqued properly after some hours on the 351, but head gaskets are not meant to be reusable and torqueing them anew after some used hours does not necessarily mean it will seal right. Who knows what this can lead to. Exhaust valves sized in their guide due to head deformation is just one possible outcome. Correct me if I'm wrong...
That being said, I am one who believes the MCM makes plenty of sense, based on the physics involved in engine hydrodynamics, particularly the intake process. Closing the intake valve at 52deg ABDC instead of 62deg would keep a greater proportion of the 250cc stroke inside the cylinder for compression, at rpms below intake resonance. But the benefits would be less for a 351 bore, as the relative resistance to flow of the intake valves becomes more important (unless they are made larger).
Take it with a grain of salt, I am no engine expert and I don't have experimental numbers to back up these beliefs.
That being said, I am one who believes the MCM makes plenty of sense, based on the physics involved in engine hydrodynamics, particularly the intake process. Closing the intake valve at 52deg ABDC instead of 62deg would keep a greater proportion of the 250cc stroke inside the cylinder for compression, at rpms below intake resonance. But the benefits would be less for a 351 bore, as the relative resistance to flow of the intake valves becomes more important (unless they are made larger).
Take it with a grain of salt, I am no engine expert and I don't have experimental numbers to back up these beliefs.
#895
03-17-2016, 02:21 AM
Help yourself to this thread: https://www.kawasakiforums.com/forum...nt-read-36129/
And this one: https://www.kawasakiforums.com/forum...s-351-a-36022/
There was a guy who successfully did the 351 + MCM and he ended up going back to stock timing.
And this one: https://www.kawasakiforums.com/forum...s-351-a-36022/
There was a guy who successfully did the 351 + MCM and he ended up going back to stock timing.
#896
03-17-2016, 04:47 AM
OK, so this revolves around "David R".. So lets look at his posts and assessments:
#193 - with intake cam only, he says his bike wants to "pull the front wheel in second" - apparently something it has never done before.. He also mentions that he must keep his intake and exhaust very quiet - read restrictive..
#172 - You gotta read this one and make your own determinations as to his assessments - My response to this post is "WTF, is it better or worse (performancewise)"...
#124 - Again, intake cam only.. He's pretty clear that he didn't like the performance in this post. However, he reports increased intake noise (growl) which would indicate he did the retime wrong on the intake cam..
Also, he was playing with his TM36 and his airbox config.. In one of the posts above, he seemed to indicate his TM36 was not functioning properly..
Everyone, who's interested, should read his posts and decide how much merit is warranted on his work/assessments.. I put none.
Certainly, however, he never experienced valve to piston problems even though he said he ran it to redline a lot..
#193 - with intake cam only, he says his bike wants to "pull the front wheel in second" - apparently something it has never done before.. He also mentions that he must keep his intake and exhaust very quiet - read restrictive..
#172 - You gotta read this one and make your own determinations as to his assessments - My response to this post is "WTF, is it better or worse (performancewise)"...
#124 - Again, intake cam only.. He's pretty clear that he didn't like the performance in this post. However, he reports increased intake noise (growl) which would indicate he did the retime wrong on the intake cam..
Also, he was playing with his TM36 and his airbox config.. In one of the posts above, he seemed to indicate his TM36 was not functioning properly..
Everyone, who's interested, should read his posts and decide how much merit is warranted on his work/assessments.. I put none.
Certainly, however, he never experienced valve to piston problems even though he said he ran it to redline a lot..
Last edited by Klxster; 03-17-2016 at 04:58 AM.
#897
03-17-2016, 07:52 PM
Now about his top post assessment here - https://www.kawasakiforums.com/forum...s-351-a-36022/
He says better power at 6k - whatever that means - but a loss of "top end" power.. What yall may not know is that he was running his own "mod" on the silencer. Apparently, a long 3/4 inch copper pipe "stinger" sticking out of the back of the poor muffler, setup to cause his poor 351 to push all its' exhaust through it.. I can tell you what that causes, a loss of top end performance !!! So perhaps his idea of less top end power was simply power levels 9k to 10.5K ( He did not specify what range he was calling "top end".) If so, it is possible that stock timings could help that range of RPM to push exhaust out the stock header and then that 3/4 inch "stinger"..
It is not out of the question that stock timings can make good TRQ numbers 9.5k to 10.5k - if so, a small benefit compared to the huge loss everywhere else..
Regardless of how well the MCM works with the 351, David R certainly did not experience problems with valve clearance.
He says better power at 6k - whatever that means - but a loss of "top end" power.. What yall may not know is that he was running his own "mod" on the silencer. Apparently, a long 3/4 inch copper pipe "stinger" sticking out of the back of the poor muffler, setup to cause his poor 351 to push all its' exhaust through it.. I can tell you what that causes, a loss of top end performance !!! So perhaps his idea of less top end power was simply power levels 9k to 10.5K ( He did not specify what range he was calling "top end".) If so, it is possible that stock timings could help that range of RPM to push exhaust out the stock header and then that 3/4 inch "stinger"..
It is not out of the question that stock timings can make good TRQ numbers 9.5k to 10.5k - if so, a small benefit compared to the huge loss everywhere else..
Regardless of how well the MCM works with the 351, David R certainly did not experience problems with valve clearance.
Last edited by Klxster; 03-18-2016 at 02:51 AM.
#898
03-18-2016, 03:22 AM
For the record: JHoffy 351 build was faulty from the start, because he did not torque the head bolts when first doing it. This is something I remember very well because it stroke me at that time. There were a few postings on the subject then. He had the head bolts torqued properly after some hours on the 351, but head gaskets are not meant to be reusable and torqueing them anew after some used hours does not necessarily mean it will seal right. Who knows what this can lead to. Exhaust valves sized in their guide due to head deformation is just one possible outcome. Correct me if I'm wrong...
That being said, I am one who believes the MCM makes plenty of sense, based on the physics involved in engine hydrodynamics, particularly the intake process. Closing the intake valve at 52deg ABDC instead of 62deg would keep a greater proportion of the 250cc stroke inside the cylinder for compression, at rpms below intake resonance. But the benefits would be less for a 351 bore, as the relative resistance to flow of the intake valves becomes more important (unless they are made larger).
Take it with a grain of salt, I am no engine expert and I don't have experimental numbers to back up these beliefs.
That being said, I am one who believes the MCM makes plenty of sense, based on the physics involved in engine hydrodynamics, particularly the intake process. Closing the intake valve at 52deg ABDC instead of 62deg would keep a greater proportion of the 250cc stroke inside the cylinder for compression, at rpms below intake resonance. But the benefits would be less for a 351 bore, as the relative resistance to flow of the intake valves becomes more important (unless they are made larger).
Take it with a grain of salt, I am no engine expert and I don't have experimental numbers to back up these beliefs.
Now about his top post assessment here - https://www.kawasakiforums.com/forum...s-351-a-36022/
He says better power at 6k - whatever that means - but a loss of "top end" power.. What yall may not know is that he was running his own "mod" on the silencer. Apparently, a long 3/4 inch copper pipe "stinger" sticking out of the back of the poor muffler, setup to cause his poor 351 to push all its' exhaust through it.. I can tell you what that causes, a loss of top end performance !!! So perhaps his idea of less top end power was simply power levels 9k to 10.5K ( He did not specify what range he was calling "top end".) If so, it is possible that stock timings could help that range of RPM to push exhaust out the stock header and then that 3/4 inch "stinger"..
It is not out of the question that stock timings can make good TRQ numbers 9.5k to 10.5k - if so, a small benefit compared to the huge loss everywhere else..
Regardless of how well the MCM works with the 351, David R certainly did not experience problems with valve clearance.
He says better power at 6k - whatever that means - but a loss of "top end" power.. What yall may not know is that he was running his own "mod" on the silencer. Apparently, a long 3/4 inch copper pipe "stinger" sticking out of the back of the poor muffler, setup to cause his poor 351 to push all its' exhaust through it.. I can tell you what that causes, a loss of top end performance !!! So perhaps his idea of less top end power was simply power levels 9k to 10.5K ( He did not specify what range he was calling "top end".) If so, it is possible that stock timings could help that range of RPM to push exhaust out the stock header and then that 3/4 inch "stinger"..
It is not out of the question that stock timings can make good TRQ numbers 9.5k to 10.5k - if so, a small benefit compared to the huge loss everywhere else..
Regardless of how well the MCM works with the 351, David R certainly did not experience problems with valve clearance.
#899
05-20-2016, 12:46 AM
Hey all, Im contemplating doing the mod on my 2009 250s, but it seems Marcelinos dyno graphs are not visible-- does anyone know where I can see them?
Im getting ready to slap on a DG O-Series , Kouba Fuel Screw, and richen the jetting.
Already re-jetted with airbox mods and drilled baffle of stock exhaust, currently running a DJ 126, stock needle w/ 1 shim, and 40 pilot jet. I started with a 135 Keihin main and the KLX 300 needle at 3 or 4 from the top, but it was WAY too rich ( I mean it would run, but gurgling and sputtering and stuff).
I dropped to a DJ 130 MJ, lowered the needle a notch, and it ran a lot better, but still felt very flat on top, had trouble getting it over 75mph on the speedo.
Current setup, bike runs very good, starts very easy and pulls strong to about 80, will top out about 85 if given enough runway and tucking in.
I have two KSF/KFX 250 Mojave quads with almost identical displacement, one with a WB E-Series and one with a DG pipe, running UNI carb clamp on filters, and they pull like animals with 135 and 138 Keihen mains. They "feel" like they have much more torque and power than my KLX, Im hoping the DG pipe will allow me to use at least a DJ 134 or Keihin 135 main. If I can get anywhere near the low and midrange my Mojaves have Ill be a happy camper. Im very curious as to how the stock Mojave timing compares to stock KLX and MCM timings. I have a Mojave service manual, Ill check it out and post my findings. I suspect its quite a bit different from stock KLX 250, just from how strong they feel across the band.
The MCM sounds intriguing, but I cant find a single dyno graph anywhere on the net. Doesnt feel right doing something like this completely blind.
Im getting ready to slap on a DG O-Series , Kouba Fuel Screw, and richen the jetting.
Already re-jetted with airbox mods and drilled baffle of stock exhaust, currently running a DJ 126, stock needle w/ 1 shim, and 40 pilot jet. I started with a 135 Keihin main and the KLX 300 needle at 3 or 4 from the top, but it was WAY too rich ( I mean it would run, but gurgling and sputtering and stuff).
I dropped to a DJ 130 MJ, lowered the needle a notch, and it ran a lot better, but still felt very flat on top, had trouble getting it over 75mph on the speedo.
Current setup, bike runs very good, starts very easy and pulls strong to about 80, will top out about 85 if given enough runway and tucking in.
I have two KSF/KFX 250 Mojave quads with almost identical displacement, one with a WB E-Series and one with a DG pipe, running UNI carb clamp on filters, and they pull like animals with 135 and 138 Keihen mains. They "feel" like they have much more torque and power than my KLX, Im hoping the DG pipe will allow me to use at least a DJ 134 or Keihin 135 main. If I can get anywhere near the low and midrange my Mojaves have Ill be a happy camper. Im very curious as to how the stock Mojave timing compares to stock KLX and MCM timings. I have a Mojave service manual, Ill check it out and post my findings. I suspect its quite a bit different from stock KLX 250, just from how strong they feel across the band.
The MCM sounds intriguing, but I cant find a single dyno graph anywhere on the net. Doesnt feel right doing something like this completely blind.
Last edited by Josh128; 05-20-2016 at 01:16 AM.
#900
05-20-2016, 01:19 AM
The originator of this thread posted dyno charts from his work with the EFI Euro version. Showed the gain across the power band. It isn't just peak HP, it's more torque all across the rpm range.
I condensed the work into a document in my signature.
I condensed the work into a document in my signature.