Harley CV Carburetor Tuning Twincam 88 

Glad it worked 👍

The same for my bike twin cam 88 2005 caughing i just shim the needle and sand paper a bit and right on perfect and thank you for the jets size and years info great my friend!

Good luck with your project, I’m sure it will work out fine.

@@aronsgarage834 Thanks! I'll be looking over your other videos for upgrades and tweaks.

Great to hear! 👍

Thanks Peter. I’m glad I could help.

I'm waiting for winter to do the work, but I'll ask you early to prepare. I have a Akrapovic exhaust, k&n airfilter with stock housing. I plan to buy the Screamin eagle big breather, what do I need to do with the carburator to get the best performance? Thank you again for your educational videos, much love.

Thanks Kim. Congratulations on your Fatboy! Wish you many happy miles! With regard to the screaming eagle air cleaner, if you do the simple tuning I showed in the video, you’ll be great.

I appreciate that! Yes, I actually made the mixture setting video back in the fall but material didn’t turn out to be good so I didn’t edit and upload. Will do it in the spring. Bikes’s still in winter hibernation 🙂

Turn the mixture screw until lightly seated. Mark the tube with a sharpie in relationship to the screwdriver blade seated flat side. Starting point one & a half turn out. Start the bike. Let it warm up all the way to operating temperature. Give it throttle. Let it settle. Turn out a half turn at a time. Let it settle. Hook up or look at your tach! Once the motor starts to idle rough turn it back until it smooths . Then turn it back again a half turn & you should be set usually. You may have to reset your idle speed. 1050 is about right depending on your exhaust and cam!

Thanks Greg.

Thanks for that. I appreciate it.

Thanks

Great! Pleased it worked out.

@@aronsgarage834 I do have an interesting thing on my Carburetor, the mixture has a fill or plug making it inaccessible. I didn’t attempt to do anything to get to it. Have you seen the his on any of the ones you’ve worked on?

Yes, of course. That’s just the factory plug. At least you know that nobody messed around with your carb before. You need to drill a small hole in it (not too deep as you can easily damage the mixture screw under it.) then using a screw extractor you can easily get it out. Do count the tuns though and record it somewhere before changing the setting.

Thanks Gary.

It might be a little lean then. Often times, just a 1/8 or 1/4 of a turn out on the mixture screw does the trick. Before you do that though, make sure you count the number of turns in until it gently seats so that you can always go back to that setting if you’re not happy with consumption or how it’s running. But if the sneezing is not bothering you, and otherwise running well, you can leave it. I would still check the spark plugs, though to make sure it’s not too lean, because that would make the engine run hotter and wear out more quickly.

Thanks for the positive feedback. It’s just a matter of bringing it down with the idle screw. Have you tried that? It should run around 850 idling cold and 1000 warmed up.

Twin Cam motors are supposed to have a slightly higher idle speed than older, EVO, Shovel motors. The beloved "potato potato" idle is for older motors. Bringing a Twin Cam idle down very low could cause engine damage, due to low oil pressure at idle.

Well, I have never tuned an Evo so this is only my best assumption: I think it could work really well, but I would use your stock jets. I believe 42 slow and 165 main?

Hey bud, I’m glad the setting worked out for you! You’ll notice that even the consumption will be great, too. I’m based in the UK (Milton Keynes) Might see you on the road in the spring 😎

@@aronsgarage834 ah cool, ya know what that would be pretty cool actually man. I'm pretty sure we could make that happen. Cheers!

Absolutely! Let me how the bike runs in the spring

@@aronsgarage834 will do mate. Tempted to go to a 46 slow jet as I'm at around 3 and a quarter turns out on the fuel mix screw. I tried just under 3 but it had a couple of moments of hesitation (carb sneezes), But soon as I hit 3 and a quarter it ran beautifully

I’ve been at 3 and 3 quarters for a while now and runs even better. Better cold idling/running and same performance. Seem to remember when I tried it with 46 it was not as good. I clearly remember though running it with 48 was really bad. Was running way too rich (sluggish) even with pilot being half a turn out only.

Thanks! I’m not entirely sure as I’ve never tuned Twincam with stage one, but I would give it a shot with this setting. If the mixture turns out to be a but weak then you could always go up in slow jet (46 or 48 even)

Thanks. I’m sure you’d need a bit more juice, bigger jets, needle maybe lifted even more. I’ve never experimented with that so I’m only guessing though.

I would go to the jet needle first because the profile of the needle can effect the off idle to 1/4 too (if you’re swapping it for the sportster 88 needle especially as the straight part is slimmer), as well as of course affecting mid range for the main part. Then you will see if the slow (up to 1/4 throttle) is enough, then lastly the main ( from 3/4 of your throttle).

45/185 or 190 jets are the standard for jetting usually depending on altitude! Because of emissions the needle dictates your fuel flow from the factory is lean. So the needle swap is where you go to & tune it all together like a EFI bike would be!!

Yes, it’s supposed to look brown or dark grey. If it’s black, you’ll end up with a lot of carbon build up on the pistons, which is not good. Yes, try to lean it a little with the mixture screw. I made a video on how to fine tune while idling. It might be helpful.

I think you’ll be alright with 3 washers.

@@aronsgarage834 I couldn't find .3mm washers anywhere but, I did find .5mm washers. Would I be alright if i install ed' 2 of them? that would be 1.0mm...also, will I be alright with stock 45 idle and 190 main jets?

Yes, 2x .5mm will be perfect. And yes, keep the 45 and 190

@@aronsgarage834 Update! You are correct when you say it's a beast. 2 of the .5's worked perfect. No hesitation at all even on slight acceleration. Top end pulls stronger too. Thanks again Bro. I'll keep on the lookout for any new videos you put out.

Great to hear the setup works for you too!

Thanks! I checked the link I put in description and unfortunately it expired but I did find the same seller I used in the UK. Click on it and see if they offer international shipping. I will also contact them to find out. www.ebay.co.uk/itm/224326415431?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=ue39x-ssq2a&sssrc=2349624&ssuid=PaL4YB6IRGm&var=523117972322&widget_ver=artemis&media=COPY

Thanks! I’m not sure about the Evo as I have never tuned one. I would leave your jets stock ( I believe 42slow and 165main?) and throw in the 88 needle without the shims. Or maybe 1x 0.3mm washer and see how it runs.

@@aronsgarage834 thank you for the fast reply, I will use your other videos foe cleaning the carb etc, great videos Aaron thank you very much!

Very welcome, Evan. I’m happy to help my fellow bikers!

What pipes are on the bike? Air filter? A 45 is good no washer under the needle!

Hi Tom, Hope you still got good riding weather in Germany :). if everything is stock I wouldn’t touch it. If you have a high flow air cleaner and open exhaust you could pretty much do the same set up. Maybe reduce the number of washers under the jet needle to 1 or 2. It’s just my assumption though as I have yet to tune a 1200.

@@aronsgarage834 it's getting cold here slowly, but sunny! what would change if everything is stock, but I work with 1-2 washers?

Hi Carlos, In the video I was showing how to tune a twincam 88 carb, any twincam between 1999-2006, so including yours. Yes, go ahead and put the 88 sportster needle in your carb with the shim washers I mentioned and your bike will run like a beast. Of course I assume your have a high flow air cleaner and open exhaust.

​@@aronsgarage834 Hi, great video! Thank you for your content and explanations. What configuration do you think would be good for the HP of a '98 FLHT 1340 with supertrapp mufflers with about 10/12 discs and open cap, big sucker arlen ness, andrews e27 cam and Dynatek 2000i ignition module? Thanks for your attention.

Thanks for your feedback! Not really sure, but I would probably try the setup I showed in the video at first instance, and see how it runs.

@@aronsgarage834 i don't have a n65c needle, but have a CV performance needle, N72S needle and N86E needle. My configuration now is: 48 pilot jet and and 185/ or 190 (i'm not sure) main jet, CV performance needle and aorun 3 and 1/4 turn mix screw. the bike seems to be running well, but how is it possible that every now and then I hear some detonation in the release of gas and the spark plugs are between white and greyish in colour? how can it be lean with a minimum of 48 and 3 and a quarter turns of the adjustment screw? ps: the dynatek setting at the third advance curve (stock motor) and single fire. I tried to put more aggressive advance curves, but the detonations increase. I can't give myself an explanation.

It shouldn’t be lean with that setting. Have you checked float level, whether or not the slow circuit is blocked, or leak around the manifold?

You can’t do it through the inlet but you can do it with the carb in place. Just lift the tank up and support it with a block of wood (posted a 2min video on this before) take the top cover off (4 screws), take out the spring and lift out the slide with the needle and retainer in there. Quick easy job.

@@aronsgarage834 Excellent, yes that is exactly what I meant ,sorry about the confused way I worded the question. Keep up the good work.

No!!

Just pull the carb out of the manifold. Lossen the choke cable. Leaving the throttle cables on it! Being it's a used bike I'd remove it anyway!!

Thanks for the feedback. I pulled some data, looks like yours had 42 slow and 170-185 main depending on model. I would try 42 and 180 combo, but if you’re over 4 turns out with the mixture screw (when running properly) you might want to bump it up to 45.

Thanks for your response and information. Regarding the needle, do you suggest I use the 3 x 6 x 0.3 shims too and how many? Also, where is the best place to source the jets you mentioned, please?

I think 2 of those shims would be enough for you. You can get jets from CV Performance (great quality) or genuine Keihin.

Sorry, it should read mixture screw 4 and 3/4 turns out.

Hi, Thanks! 1200 Sportster is a great choice! What do you mean about doing oil separately for the carb? Yeah, mine looks very clean. I did put it through my ultrasonic cleaner, but a carb cleaner spray will do the trick inside and outside. :)

@@aronsgarage834 I founded. Is the one you have in your bike catch can air oil separate Thank you

@@Ruffles206 oh you meant the crankcase vent. Yes, it now goes into a catch can I made. I will make a video on how to make one in the future.

I order this kit for my sportster 1200 custom Drag Specialties Breather Kit For Harley Sportster 1991-2022.I start doing today and I found out that the plastic cover the one hold the carburetor that’s doesn’t fit with kit, you’re air cleaner is smaller. Do you know or found a video how this kit works?

@@aronsgarage834 how does your catch can vent you have a rubber cap on your exit side of catch can and breather vent hose going to catch can entrance ? or am i just Stupid?

Ebay. If you type in shim washers classic cars/ motorcycles it should come up. I think I put a link in the description too. Let me know if you can’t find it.

Thanks. Not entirely sure because you have different cams in there but would definitely be my first choice of set up. Try it and see how it runs..

One last question. Finding the correct washers is difficult in the USA. I assume the id of the washer needs to be very close to the needle diameter? So far the washers I’ve found are loose.

Yes, should be quite close. If you are struggling to find the right size, I’ll send you some. Send me a message on Facebook. Aron vetesi

@@aronsgarage834 Aron, that would be awesome. But I’m in the USA. I can Venmo or PayPal in advance for postage if you are still willing.

@@gnoub51 send me a message on Facebook and we’ll get it sorted. Aron Vetesi

Hi Peter, Funny you should ask, I’m about to do that one. I ordered in the parts for it. I’m just waiting for the rubber end plug/cap to arrive. Hopefully next week I can do it.

@@aronsgarage834 tnx for responding! I’see forward to it. Greetings

That’s likely to be a 48, however it is only my assumption. I would put that in and do the fine tuning with the pilot screw at idle. Should fall between 1.5 and 2.5 turns out with the 48. Let me know how it turns out!

@@aronsgarage834 Thanks! maybe tomorrow.

How many shims would suggest?

I would go with 3 shims.

Hey Aron, just a little follow up, This bike did already have a #48 in it, I installed the N65C jet with 3 shims, air screw turned out 2 turns and I am very pleased with the results. The bike starts right up, warms up quicker, pulls strong, and does not shake as much at idle. I am going to tune on the air screw a little to get a little better throttle response on the bottom. but all in all I am thrilled, Thank you!

Mine is 3 & 1/2 currently. 1 & 3/4 and 2 turns out were factory standard. These bikes were set too lean to start with. Then like most of us, we put high flow air and open exhaust on, so need to adjust. The 3 - 3 & 1/2 sweet spot applies only if you’ve done those small mods and your carb has stock slow jet (45).

You’re most welcome! You can get it from BigBoar if you’re in the UK or Ebay. Usually around £35.

3ㅡ3

Thanks. Not sure as I didn’t experiment with those needles, but since it’s a performance needle, you shouldn’t need any shims.

@@aronsgarage834 I checked their website. No shims required, just drop in and run it.

Yeah, that’s what I thought.

@@aronsgarage834 I've got 2 on order for both my bikes.

Hi Brad, the 48 and is too big. You’d have a sluggish performance being too rich. I’ve tried it before. 46 is ok but honestly you’re good with stock 45. Just adjust the pilot screw after installing the air cleaner. Give it an extra quarter or half turn out. Or better yet, perform a fine tuning while bike idling and you’ll find the sweet spot. I’m actually in the process of uploading a video on that.

@Aron's Garage So you mean adjust the mix screw since you can't adjust the pilot jet..

Yes. Do check and record the setting first, though by turning it in until it gently seats counting the turns. This way you can always go back to that starting point in case you lose track of turns while fine tuning it. Mine is at 3 and 1/4 out with high flow air cleaner and modified stock pipes/ or screaming eagle.(of course I have the thinner needle set up too as shown in my video)

@Aron's Garage I bought the cv Performance kit from the cvo website.. So, I will be replacing the needle and adding the t tall mixture screw .

Got you. You should be all set then.

You can pull it out of the piston and using a bit of soapy water you slide the new one back in place while giving it a little stretch. I did it a couple of years ago and ran it with no problem, however I decided to replace the slide as a unit because I learned that replacing only the diagram is not really recommended by factory. It may not function 100%.

Unfortunately I can’t find a good link, but if you search for Harley Davidson CV carburetor keihin needle jet, you should be able to find it. Or go to your local bike parts store and they should be able to look it up for you.

@@aronsgarage834 I found a Harley Davidson CV carburetor keihin needle beam, but I can't see the 2.8mm part separately!

The needle jet is the part with a 2.8mm hole. It’s one part

@@aronsgarage834 I got a 130mm long sliding spring in the set. Do you know an article number that gives the requested 143-146 mm? The other parts are there, only this is different.

The part number I got is 27162-89. I have noticed though, they still come in different lengths sometimes. Even the dealer couldn’t verify why that was.. Hope it helps

Ebay. Carb jet driver set. I put link in description.

You are right. My 99 Superglide was fitted with 42 slow and 185 main. I understand most 88s did come with 45/190 after 2000, though. Frankly, 42 was really lean especially with high flow air cleaner and open pipes.

In my neck of the woods 48 slow 2000s . What’s your opinion?

Don’t use the 42. I have it on mine currently. The carb is new and I was gonna see how it performed going that low. Bad. It’s not even rideable. I almost dumped it from the lack of power making city turns. practically stalling it in a few turns. I’m putting 45 in and tuning from there. Top end is good on mine with the 170 main jet. I might try increasing it after I get the idle mixtures set good. The needle is stock but I might try that 88 sportster needle you were talking about.

That’s most likely because it’s too lean. What set up do you have in your carb? How long has it been doing it? If only recently, it may have developed an air leak around the manifold or vacuum hose or around the air-cleaner. It could also be a clogged slow jet in your carb..

@@aronsgarage834 my carburetor is a cv carburetor also I just recently changed out the Jetts and I have the air fuel screw turned out 1 5/8 and it does sound like I have a rear manifold leak it does this crackling sputter sound from the rear head.

Cool. Let me know if you’ve found the leak

@@aronsgarage834 yes I did find the leak it is off of the rear head. One of the exhaust manifold gasket studs busted so now that's my situation I like working on my own bike but sometimes I get tired of not being able to find help lol anyway thank you for responding

That’s great, I’m glad you found it. Yeah, that’s what I like about our “Harley community” that we stick together and help each other out. Have a good one

Sure, Carlos. It’s called a carb jet driver set and JMP is the brand. I bought it on Ebay. I put the link in the description of the video.

4 mm allen bolts. I find it easier with them. Plus it’s easy to carry an allen key in the pocket or toolbag in case you run into an issue on the road.

@@aronsgarage834 Thank you for your response! do you happen to know the length of the bolts?

Sure. It’s 16mm for the cover, 14mm for the float bowl and 8mm for the accelerator pump.

@@aronsgarage834 Thank you so much for your help, and for this incredible video. I appreciate the effort you put into the video and it's been incredibly helpful.

Thanks very much for your positive feedback.

Stock cam.

What state are you in, Rick?

@@aronsgarage834 I'm in Missouri. That was a Great video you made, I'm trying to do mine EXACTLY like you did it in the video. Mine won't idle down after riding it while hot, so I assume someone has drilled out the slide. Thanks Again

@@1rottenrat yeah, measure the port hole on slide. You might need a new one if drilled. It’s also worth getting a brand new good quality 45 slow jet (in case it was messed about too, and got enlarged) In regards to the washers, if there isn’t on Ebay US, call up hobby model shops, they should have these small shims. If not, let me know before Friday. We’ll be travelling to Vegas and I could just post a few to you from there.

@@aronsgarage834 I bought a new slide and a set of new jets just like you described in the video. Thanks for responding so quickly. I greatly appreciate your help on this, again the video was EXCELLENT.! If I can't find them I would gladly send you money for them and the postage. Thanks again.

@@1rottenrat Super! I’m glad it’s helpful. Yeah, let me know if you can’t find them, happy to help.