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Author Topic: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!  (Read 3991 times)

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Offline rshinall

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So it seems that most folks recommend the Denso X24ES-U over the NGK D8EA. I've done a LOT of tuning on the bike over the past few weeks, and she is running very well. So I figured I would put the cherry on top with the X24ES-U plugs.

I installed them and went for a ride, and I was very disappointed. For me, there is a significant difference in how the bike performs with the Densos - it seems sluggish, and throttle response is poor. But only with the X24ES-U plugs. With the good ol' D8EA plugs it was fine. Am I the only one with this experience? Ultimately I guess it doesn't matter - I will use what works best. However, it is puzzling to me. I'm in Florida but the weather is still cool and humidity is pretty low right now.

Tomorrow morning she gets D8EA plugs!

Thoughts?

Offline Reganator

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #1 on: April 23, 2013, 08:14:14 PM »
Tell me more...

The Denso's were recently recommended to me.  I've ordered a set but have the NGK plugs in at the moment and I'm starting to doubt I'll put the Denso plugs in only because it seems to be doing so well with the NGK plugs. 

I'm sort of new to this whole motorcycle thing though, so I'd love to hear more on the subject...
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Offline tomkimberly

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #2 on: April 23, 2013, 08:22:49 PM »
Who are "most folks"? I run NGK in all my bikes.


Tom


Offline HondaMan

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #3 on: April 23, 2013, 08:30:23 PM »
I'm curious to hear more, too: in 100% of the SOHC4 bikes I have built or tuned for the last 40 years, the ND plugs have beat the NGK for performance and smoothness. Honda now boxes these as their OEM parts.
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Offline goldarrow

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #4 on: April 23, 2013, 08:47:22 PM »
I just bought a box of 10 ND x24es plugs for $20 shipped. 
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Offline bryanj

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #5 on: April 23, 2013, 10:35:38 PM »
Here in UK Denso are more difficult to find and I have never had a problem with any NGK. On my old 500 in the late 70's I fitted the EV ngk type and instantly got cleaner running and more MPG(but not much more) plus it felt like quicker pick up, not sure it was worth the 4 times price premium but the first set were a "Gift" from the NGK rep, an old racer called Stan Dibden.
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Offline MoMo

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #6 on: April 24, 2013, 01:32:04 AM »
Back in the 70's the single, easiest thing that improved performance(and reliablility) was removing the Denso and intalling NGK.  My experience with Denso plugs has not been good at the three shops I worked.  My .066...Larry
Present: 1975 CB750, 1974 CB750, 1975 CB400 four,  1966 Suzuki S32 150cc , 1984 Honda Sabre, 1998 Pacific Coast (my daily rider) ,  ALL FOR SALE EXCEPT THE SUZUKI!

Past: Two Honda XL125s )(I rode one in enduros), Honda XL175, Yamaha DT1, MZ 250 ISDT, Harley Hummer, 1969 Honda CB350, 125 Sachs/DKW, 250 Ossa Pioneer, 1968 250 Montesa La Cross, Yamaha RD350, two Yamaha TX500, eight Honda CB450 dohc, 250 KTM, 1982 Yamaha 650 four(worst bike ever owned), seven Honda CB400f's, 1983 Honda VF750F Interceptor, 1981 CB650, 1973 CB350G, two 1973 CB750s, mint 1975 Honda CB550F, two 1977 CB750K7s , two GL500I Silverwings, 1973 Jawa 175 Trailmaster, SL350 K2, 1970 CB750K0, 1972 CB350, 1974 CZ 250 Enduro, and  probably others long forgotten.

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #7 on: April 24, 2013, 01:39:31 AM »
i consider the denso and ngk as the same?not one over the other?there has been fake denso and ngk plugs sold and they have the packing almost the same,,try and be sure this isnt your case!ngk and denso and any other brand of anything will fiercly fight any ripp offs,,i find bosch a bit colder per number and we wont even mention champion,you will never have any trouble with denso or ngk in the correct heat range for any engine.
« Last Edit: April 24, 2013, 01:41:05 AM by dave500 »

Offline HondaMan

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #8 on: April 24, 2013, 09:57:56 PM »
Back in the 70's the single, easiest thing that improved performance(and reliablility) was removing the Denso and intalling NGK.  My experience with Denso plugs has not been good at the three shops I worked.  My .066...Larry

When it came to the old ND standard plugs", I agree: they seemed like cheap plugs and sparked weakly. The difference came in 1973 when they created the new series they called the "Hot U" (that's the "-U" on the end of the part number). I still think the U-shaped ground arm of these plugs is a gimmick used to delineate them from their other offerings, but the electrode and ceramic above it are very different from the 'original' ND plugs. Those old ND plugs had very thick, short ceramic noses and steel center electrodes, both a cheap design. The "Hot U" plugs have a thin, long, fine-grained ceramic with an alloy electrode that does not expand with heat, hardly at all. The seal in these plugs is the tightest I have ever seen, even at 10k PSI tests they don't flake, powder, or flex. This means the metal body is also either tensile or heat-treated, not a cheap process.

I suppose I could go on for another few pages about sparkplugs, but will hold back until it is in my book.... :)
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Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Offline MoMo

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #9 on: April 25, 2013, 03:20:17 AM »
Back in the 70's the single, easiest thing that improved performance(and reliablility) was removing the Denso and intalling NGK.  My experience with Denso plugs has not been good at the three shops I worked.  My .066...Larry

When it came to the old ND standard plugs", I agree: they seemed like cheap plugs and sparked weakly. The difference came in 1973 when they created the new series they called the "Hot U" (that's the "-U" on the end of the part number). I still think the U-shaped ground arm of these plugs is a gimmick used to delineate them from their other offerings, but the electrode and ceramic above it are very different from the 'original' ND plugs. Those old ND plugs had very thick, short ceramic noses and steel center electrodes, both a cheap design. The "Hot U" plugs have a thin, long, fine-grained ceramic with an alloy electrode that does not expand with heat, hardly at all. The seal in these plugs is the tightest I have ever seen, even at 10k PSI tests they don't flake, powder, or flex. This means the metal body is also either tensile or heat-treated, not a cheap process.

I suppose I could go on for another few pages about sparkplugs, but will hold back until it is in my book.... :)



Guess I'm still living back in the 70's HM ::).  Once I find something that works I rarely change, maybe I'll give the NDs a shot but I can get NGK at the local parts distributor for a shade over $2 and they have given me many years of reliable service...Larry
Present: 1975 CB750, 1974 CB750, 1975 CB400 four,  1966 Suzuki S32 150cc , 1984 Honda Sabre, 1998 Pacific Coast (my daily rider) ,  ALL FOR SALE EXCEPT THE SUZUKI!

Past: Two Honda XL125s )(I rode one in enduros), Honda XL175, Yamaha DT1, MZ 250 ISDT, Harley Hummer, 1969 Honda CB350, 125 Sachs/DKW, 250 Ossa Pioneer, 1968 250 Montesa La Cross, Yamaha RD350, two Yamaha TX500, eight Honda CB450 dohc, 250 KTM, 1982 Yamaha 650 four(worst bike ever owned), seven Honda CB400f's, 1983 Honda VF750F Interceptor, 1981 CB650, 1973 CB350G, two 1973 CB750s, mint 1975 Honda CB550F, two 1977 CB750K7s , two GL500I Silverwings, 1973 Jawa 175 Trailmaster, SL350 K2, 1970 CB750K0, 1972 CB350, 1974 CZ 250 Enduro, and  probably others long forgotten.

Offline flybox1

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #10 on: April 25, 2013, 06:54:59 AM »
Denso's at Rock Auto - $1.32ea  ;)
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Offline 736cc

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #11 on: April 25, 2013, 07:05:47 AM »
New NGK's and ND's are both ALOT better than used plugs.....
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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #12 on: April 25, 2013, 09:39:51 PM »
Back in the 70's the single, easiest thing that improved performance(and reliablility) was removing the Denso and intalling NGK.  My experience with Denso plugs has not been good at the three shops I worked.  My .066...Larry

When it came to the old ND standard plugs", I agree: they seemed like cheap plugs and sparked weakly. The difference came in 1973 when they created the new series they called the "Hot U" (that's the "-U" on the end of the part number). I still think the U-shaped ground arm of these plugs is a gimmick used to delineate them from their other offerings, but the electrode and ceramic above it are very different from the 'original' ND plugs. Those old ND plugs had very thick, short ceramic noses and steel center electrodes, both a cheap design. The "Hot U" plugs have a thin, long, fine-grained ceramic with an alloy electrode that does not expand with heat, hardly at all. The seal in these plugs is the tightest I have ever seen, even at 10k PSI tests they don't flake, powder, or flex. This means the metal body is also either tensile or heat-treated, not a cheap process.

I suppose I could go on for another few pages about sparkplugs, but will hold back until it is in my book.... :)



Guess I'm still living back in the 70's HM ::).  Once I find something that works I rarely change, maybe I'll give the NDs a shot but I can get NGK at the local parts distributor for a shade over $2 and they have given me many years of reliable service...Larry

Yeah, I understand! I used the NGKs (only) myself from 1964 until 1973. On some of the Japanese bikes there is no good alternative, like the C70 or CT70/90 engines, as the HD heatrange is slightly hotter in those cases. Recently, I have found the ND plugs even cheaper than $2 each, which surprised me (on line). Here at O-Reilly the NGK are $1.99 each.

But then, the situation for the 750/500/550 is also a little unique: the original D8E heatrange in 1969 was hotter than the later "S" versions. The D8ES first appeared in 1970 and was touted to be "Super-wide" heatrange #8, supposed to be good for hiway and in-town riding. In reality, they simply improved the powder seal around the ceramic so it would not burn out at prolonged hiway speeds (improved the heat transfer to the head, cools the tip more), but it turned out to not be hot enough in city riding on the 750. This became a big enough problem that Honda used the D7ES in the CB500-4 from the start (and all subsequent Mid-Four engines), as it would not burn out at speed, but kept the smaller engine's plugs cleaner. It also burned up the exhaust guides faster from the increased heat on the exhaust valves, though. So, the valve guides were made gigantic on the Mid-Four engines, to help cope with that issue.

Then, the US suddenly had a 55-MPH speed limit! This put the 750 barely above its plug-fouling range when toured in high gear. A D7 heatrange plug was too much for the smaller 750 exhaust guides, though. ND answered Honda's request for help by creating the X24ES in Japan and Europe, an extended-tip plug with thinner ceramic tip that would burn off deposits better while sinking D8-like heat to the head. It is interesting to note that NGK (owned 100% by ND Tokyo, even today) came out with the D8ES-L about 4 months later, for the US market where NGK was touted as a "better" plug (it must have been? After all, it cost 3x as much as the ND plug...). Truth was, the 'best' plug for the 750 then was proving to be a Bosch plug or the Champion, but Honda dealers were forbidden to use them on bikes in warranty (!) to solve the plug-fouling issues (we did it anyway...). Interestingly enough, by 1980 the X24ES-U dominated the touring market in these bikes about 3-1, and Champion and Bosch both dropped their plug that was targeted at the market by about 1984 or so.

Today, with ethanol-laced gas, the D8E heatrange is again too cold for anything but 70+ MPH touring. The ethanol runs much cooler than the old gasolines. On in-town bikes here in Colorado, I am finding the NGK D7 to be fine until one heads out on the road, where it tends to build up head heat after 50 miles or so of 70+ speed. This is where the X24 comes into its own again: it is approximately an imaginary D7.6 heatrange if directly "converted" to the NGK scaling numbers, somewhere between the D7 and the D8.

So, just to make all this more obscure: in 1996 the EPA threatened to fine NGK for claiming the "Super-wide heatrange" in their ads, saying that it was physically impossible to meet these temperature extremes with one plug (honest! I have the article around here, somewhere...). The EPA actually forced NGK to make the D8ES go away in favor of making it colder, and spec a narrower temperature range for it, and they had to relabel it "D8EA". I still don't know why the A" designation, despite nearly a dozen supposed explanations for it. What I have observed, though, is this: the D8EA is almost as cold as the old D9E plug, and it similarly will not clean its tip for beans. If it gets dirty, you must change the plug or sandblast the tip clean, as it will no longer burn off the deposits by itself. By this, you can be sure it is colder than the old D8ES was: despite many words, the proof is in the riding! :D
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

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Offline david 750F

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #13 on: April 25, 2013, 11:55:53 PM »
Hondaman, here in the Canada (the great white north), The Honda dealer still has D8ES-L's for $2.50..That plug works great in my 1976 CB750F.
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Offline rshinall

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #14 on: April 26, 2013, 03:21:10 AM »
HondaMan, that is some great history. Thanks for sharing that!

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #15 on: April 26, 2013, 06:27:14 AM »
HondaMan, that is some great history. Thanks for sharing that!

Hondaman Yes thanks Now I don't know what plug to use ;D ;D I don't drive in the city at all. On my back roads I drive in 5th gear and keep in at or a little above 3000 below that I drop to 4th. don't want to lug it. Now what plug would you use for that?
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Online dave500

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #16 on: April 26, 2013, 01:29:56 PM »
stay above 3500-4000.

bollingball

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #17 on: April 26, 2013, 02:19:51 PM »
stay above 3500-4000.

Thanks Dave. I know you are a 500-550 guy but what plug on my 750 with my type of driving would you use and I will start keeping it up at least 3500 Also at 3000 it sounds good no luging if I do need to scoot around a car I drop it down to 4th or 3rd
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Offline 70CB750

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #18 on: April 26, 2013, 02:32:42 PM »
I have 17/48 sprockets and the rpms for local roads are 3500 - 4000, I like it.
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bollingball

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #19 on: April 26, 2013, 02:43:20 PM »
I have 17/48 sprockets and the rpms for local roads are 3500 - 4000, I like it.

What year? My 78K came stock 15-41 I just took the front one off and saw the PO had a 14-41 and I am going back to stock 15-41 can not remember what the larger front will do to my rpms or speedo. I lost all my Honda files from a virus.
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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #20 on: April 26, 2013, 09:44:29 PM »
I have 17/48 sprockets and the rpms for local roads are 3500 - 4000, I like it.

What year? My 78K came stock 15-41 I just took the front one off and saw the PO had a 14-41 and I am going back to stock 15-41 can not remember what the larger front will do to my rpms or speedo. I lost all my Honda files from a virus.
Ken

It will cause you to tend to drop down one more gear, on average. I use the 17T/48T (530 chain size, yours is 630, so different tooth counts) in town so I can just 'touch' 4th gear at 40 MPH on a 110/90 rear tire size. If I use the OEM 18T front, the engine dislikes 4th gear until 45 MPH minimum. For your comparisons, just use the ratios: divide (REAR/FRONT-RATIO) and use the number to 3 decimal places so you have the same references.

All this aside: the beauty of the D8ES-L and the X24ES-U are that their tip stays hotter at a lower engine speed. This means the 750 is able to tolerate more of the 3000 RPM low end, and the post-1975 cams become smooth and torquey right about there, to redline. The earlier cams opened sooner, so the RPM need to stay higher, like 3500 RPM, before the smoothness and torque start. Their midrange torque arrives sooner, too (like 6000 RPM), so the original design was for 3500-6500 nominal running range, where the D8E plug "lived". When the gearing kept getting taller to reduce chain wear issues, the RPM tended to drop in use, so the hotter plugs had a new home. But, the D7E suffers the same 'turndown ratio' as the D8E, so if you run along at the 2500-5500 RPM range (i.e. 3000 RPM span) of that #7 plug, you find a hot exhaust guide at constant hiway speeds of 5500 RPM. The D8ES-L ("L" means "Longer tip") and the unique X24ES-U "womanly" design, as we called it back then (meaning: shapely!) produced the in-between temperature range that fits just right. (Why does this sound sultry?...).

I find it interesting that NGK was tapped in the early 2000 era to produce the DR8ES-L for the modern sportbikes with their CDI systems. I also find it interesting to see how many of those bikes are using the XR24ES-U instead, at least around here.

Hondaman, here in the Canada (the great white north), The Honda dealer still has D8ES-L's for $2.50..That plug works great in my 1976 CB750F.

That's cool! Around here we can only get the DR8ES-L version. It is only 2000 ohms, but it does raise an interesting point: the OEM Honda coils and plug caps are set for 7500 ohms between the coil and plug. The modern NGK plug caps are either 0 ohms (not good for these bikes), 5000 ohms (adequate, but not nominal), or 10,000 ohms (which proved to not last well on the post-1975 bikes). So, if you were to use the XR24ES-U or the DR8ES-L with the 5,000 ohm plug caps, this would be very close to the original spark setup, at 7000 ohms.

What this means in English is: since the Honda coils were meant to discharge into 7500 ohm resistors to obtain a 1.5mS duration spark, and since the 5,000 ohm plug caps are a little less than that, you get a slightly shorter spark of about 1.43mS (mathematically, anyway...and felt in the butt dyno). If you use both resistor plugs and 5,000 ohm caps, you can get the 1.5mS back. In the lean-burn post-1976 bikes with PD carbs, Honda 'stretched' the spark of the same coils to about 1.6mS with 10,000 ohm plug caps to help ignite the harder-to-start lean mixtures (for EPA reasons). The trouble was: the resistance is high enough that any slight crack or 'tracer' growth (from dirt or moisture), or even a cracked rubber boot, lets the spark jump to the engine and not the plug. So, the later spark caps "burned out" much faster than the earlier ones. Often, the rider would opt for the Dyna 3-ohm high-output coils to "fix" this, accidentally replacing the plug caps in the process, and receiving a temporary performance boost for his effort: hence the early-on perception that the high-output coils were an improvement, when replacing just the plug caps would have made a BETTER improvement, all else being equal...but, that's history now. :)
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #21 on: April 26, 2013, 10:32:54 PM »
just keep your rpms up,the engine will be ready to respond without a down shift,and you will be riding as it was  designed to be,no matter what sprockets your running,,you should be feeling this "just under the sweet spot" rpm anyway without a tacho?dont be scared to rev these engines no matter what sohc four high rpm jewels you have,,they will spin happily all day at 6000 plus some,dont try to cruise them too much,,this isnt where they work well,thats where plugs foul,the whole thing isnt operating at its designed rpm,the combustion temp is too low,sure you can trickle along through traffic then pull away still in top gear but only for so long,down shift it and really ride the bike.

Offline 70CB750

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #22 on: April 27, 2013, 04:02:20 AM »
It is 1970 with homemade airfilter, Pamco, hotter coils. Not sure what jets, but the needle is at #4.

I am very happy with the overall combination. It ran ok with pods when I got it, but I made it (I believe :)) run better.
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Work smarder and not harder and be careful of yor speling.

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Online dave500

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #23 on: April 27, 2013, 04:21:15 AM »
my post goes for all these bikes,,and does apply to all readers,,keep your rpm up somewhat and be better off!keep the engine on the boil,if you let the torque sag off itll be a two gear down shift to reclaim it,,anyone who doubts me is lugging their engine full stop,,period!
« Last Edit: April 27, 2013, 04:23:28 AM by dave500 »

Offline 70CB750

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Re: CB350F spark plugs: NGK D8EA vs. Denso X24ES-U - don't like Denso!
« Reply #24 on: April 27, 2013, 06:02:49 AM »
Spot on, Dave, the kick at 4000 rpm always makes me smile.
Prokop
_______________
Pure Gas - find ethanol free gas station near you

Work smarder and not harder and be careful of yor speling.

Dorothy - my CB750
CB750K3F
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