Still considering swapping out my yuminahsi cam.. I like the idea of a DCR cam but was never a fan of regrinds (from back in the car days) .. but also like the specs on the Yosh cam as it def seems more aggressive. .
has anyone compared the 2 to each other? on a 164-170 setup with usual trimmings. (exhaust, fuel controllers, etc)
With a 170 I'd probably swing for the 170 specific DCR cam.
I just had an Brian S. 170 bike with a regular DCR cam on the dyno and it made a flat 14hp from 6500-9000rpm. The larger DCR cam has ~10* more duration and a bit more lift as well.
Did that bike have a stock head or a Brian S Ported head? I have a Brian S 170 kit DCR cam and PCV WB2, m4 exhaust and K&N Intake. I've never had it Dyno'd and always wondered what it put out. Feels pretty good but I'm thinking of getting The Brian S head too
heres the specs i have gathered in the same units:
DCR: duration is 224 degrees with .208" lift (in/exhaust)
Yosh:
225 intake degrees with .246" lift
220 exhaust duration with .246" lift
for sake of comparison:
stock grom cam specs:
204 degrees intake with .192" lift
200 degrees exhaust with .190" lift
I am aware some lower profile cams can work better than big lopey ones... hence why i wanted to hear soem feedback on the 2 for those who have tried both.
so 10-15 degrees longer duration but less lift (.020") than the yoshimura one. i bet thats a lopey bastard. I hadn't seen that one yet. midrange must be awesome on that. so you compared the 1st dcr i listed to the yosh one ? or the big bore DCR cam?
The bike I compared first had the first DCR (less duration) cam in it. The problem with the first DCR cam in the 170 bike is that it falls on it's face at 9000rpm. After we ported the head it did a little better but still takes a dump up top. I've been trying to get my buddy to purchase that BBK Cam but he doesn't want to shell out the cash right now. I'm sure the extra duration would help out up top.
makes sense. I have a yosh cam coming... again, not a huge fan of regrinds. I paid 215 shipped for it so we will see.(it son its way) what i plan on doing is taking the yuminashi cam out and comparing the 2 with a dial indicator on my lathe to see what exactly i have in there.
My head is ported (me) and runs pretty strong as it is, im happy with it. but on such atiny motor small changes make big differences in valve timing and duration. It seems the dcr/yosh cams are pretty comparable spec wise.. if the yosh didnt exist i would go with the reground dcr. maybe i will eventually.?
intersting. well i still have the stock rev limit +500 rpm so midrange is good. going to be curious as to how it performs over the yuminashi.
the differences seem minor in power delivery peak VS where int eh rpm range it hits.
Yosh
DCR
the dcr seems to have a longer spread over 7.5 but there are assuredly other factors in play here. Hence why i was asking for a back to back with all else basically the same.
as a follow up to this.. i found a few interesting things. I received the yoshimura cam shaft and did some comparisons to the Yuminashi cam that i have had.
1: the lift of the yuminashi cam is quite a bit greater. at the lobe measurement it is ~0.65 mm higher.
2: the duration is much greater on the yuminashi cam. I didnt even measure it fully , you can see it. but as i was measuring the lift i would say its a good 15 degrees greater.
3: in the attempt to try toe yosh cam, i learned that the longer valves required for the yuminashi cam did not allow the installation of the yosh cam. the min diameter of the cam is too great and it could not be adjusted (the exhaust rocker would not go on even adjusted all the way 'out'
4: by the looks of things, the yuminashi cam is much more aggressive. I wanted to try the yosh cam but will not take the head off to replace the valves as a test.
so, looking at the specs of the dcr and the yosh VS the yuminashi, it appears the most aggressive cam is the yuminashi one. this surprised me. I re-installed the yuminashi cam and stored the yosh cam back in the box it came in.
for those wondering, i measured the cam lift on my lathe with a live center and a metric dial indicator.
I didn't realize you had a built Yuminashi head. I ran in to the same problem trying to fit my Yoshi cam in to my Finbro head with longer valves. The Finbro cam that came with my kit was also MUCH more aggressive than the Yoshi or DCR, but with my smaller 147cc bore it was very peaky and didn't start making any power until after 8000rpm. I inquired on the specs and was told that the duration of the Finbro cam was 250* and that it's the same cam used in the 183cc kit (which seems to work fine with that). I ended up using a DCR cam (the fact that it's a regrind helped me haha) as it was the only other cam that would fit in the head, and it helped me get some low end power back.
If you're bike has a built head and it's a 170, the Yuminashi cam, 170 DCR, or the new 170 KOSO cam will probably be best.
I know very little about grom performance, but I know a little about cams. And to compare duration from one brand to another can be misleading as they do not all use the same lift starting point to measure duration.
And for real fun you could find a way to degree the cams in a grom and then be able to shift the power up or down slightly in the rev range. But this is a lot of work often for no real benifit...lol
That is why you R n D
Take shit out and replace it with more shit to see if it works or improve HP, if not you take the shit back out and start again.
HP is not only the biggest, newest parts but the total of the whole that will improve HP. Starting with rider wt, if you are FAT you will go slower or go off the line later, that is why skinny riders with the same HP as you will get the edge jump at the starting line
Reaction time also plays a lot in winning or getting the edge.
Gearing also needs to be checked so does tire size and tire pressure.
At the end the person that tunes his MC for that track or race day properly will have the edge if all other variables are the same with the other riders Grom/MC
if you are going to pull the head, youre a wristpin away froma big bore. and you can get a small kit from webike for like 200 bucks. 133/143/164 etc. why not take the plunge?
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