I can understand how economics play a part. They won't be ideal while the engine is stock (I'm imagining leanness with an open throttle and low rpms) but I'm sure you'll get them working well enough to do the job. Still, it sounds like a fun project.
Mikuni Carbs on Holden 6?
Started by
_gthr_
, Apr 29 2010 01:19 PM
34 replies to this topic
#27
_triumph202_
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Posted 05 June 2012 - 04:56 PM
Seeingi though you have your mind made up do as you wish
Cheers.
Well, technically, I wasn't asking for any opinions on the mod- I just said I was considering it. It's still in the consideration phase.
Besides, if everyone followed the same path life would be pretty boring.Out of interest John (?) from V-Performance has recommended twin HSR45's, "given the engine capacity and plans for future engine mods." They've converted quiet a few vehicles.
#28
_triumph202_
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Posted 15 June 2012 - 10:14 AM
So how did it turn out? I'll most likely be sticking with SU's - I've tracked down a full rebuild kit (from the UK) for about $115 for twin HS6s. That includes the bushings for the worn housings, new spindle, float needle / seat etc. And it's about $12 to convert both from Waxstat jets to standard jets; I waiting for a price on needles....I am just completing my 202 with the 42 HSRs and at this stage it looks like it will be started Wednesday. I will let you know how it goes although I will have nothing to compare it to.
Edited by triumph202, 15 June 2012 - 10:16 AM.
#29
Peter UC
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Posted 15 June 2012 - 11:11 PM
Just went for my first drive tonight after running the cam in on Wednesday night and it starts and idles fine, goes pretty well, still early days and I'm trying to bed the rings in so I'm driving like a tool. Tune needs a bit of work through the mid range where it gets a bit lean through the transition, but full throttle is about 12.5:1 so not far off, but it should be only a few tweaks away. Carbs are dead simple to tune so there are no problems getting it right, plus I put in a wide band sensor and guage to make my life easier. I'll do a bit of a write up when I'm happy to show how it's set up and the tune I put in it.
#30
_ljxu1torana_
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Posted 16 June 2012 - 01:06 AM
if you want to bed in your rings is either at 60 km/h in top gear then accelerate,or drive up a range in top gear.this means is to put load on the motor.thanks jason.Just went for my first drive tonight after running the cam in on Wednesday night and it starts and idles fine, goes pretty well, still early days and I'm trying to bed the rings in so I'm driving like a tool. Tune needs a bit of work through the mid range where it gets a bit lean through the transition, but full throttle is about 12.5:1 so not far off, but it should be only a few tweaks away. Carbs are dead simple to tune so there are no problems getting it right, plus I put in a wide band sensor and guage to make my life easier. I'll do a bit of a write up when I'm happy to show how it's set up and the tune I put in it.
#31
_sherpa_
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Posted 22 June 2012 - 01:36 PM
Over the last ten years or so I have fitted flatslide carbies to several offroad motorbikes and without exception every conversion has been a big improvement. Each time the standard round slides [mikuni, dellorto and amal] were replaced with a flatside and no other changes. I have used Keihin , Mikuni and Dellorto flatslides and although they are very similar I would say the Keihin was the best. The mikuni and dellorto look to be better quality but the Keihin just seems to work that little bit better.The Dellorto was the hardest to jet, which is unusual as their round slides are possibly the easiest and most consistent. Keihin and Mikuni jets and parts can be purchased from Show and Go[in SA in think]one day turnaround on orders. Overall performance increase [seat of pants feeling] would be in the order of 15%. The off idle response is cleaner and crisper, the mid range hit is bigger and they rev harder, in other words better everywhere. They also are a little easier to jet, the only downside is they use a fair bit more fuel, as these are competition bikes that is not a problem.
Cheers Greg
Cheers Greg
#32
_Sir LC_
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Posted 28 August 2014 - 09:42 PM
Hi Peter,
How have you found the Mikuni's, any useful tips you could pass on?
I've been doing a bit of reading on the mikuni's and contemplating getting some for the straight 6, either the 3 or 6 carb setup.
My mild 186 will need some work to make it worth it, but like yourself I want to get something that serves the end goal.
Its been mentioned that if tuned IR manifolds are not used, than SU would be a better option - is anyone able to provide any advice on where to go/look to get such a manifold made (and done correctly)? Is this a costly exercise? (trying to work out how much it would cost to do).
Any info would be great, cheers!
Just went for my first drive tonight after running the cam in on Wednesday night and it starts and idles fine, goes pretty well, still early days and I'm trying to bed the rings in so I'm driving like a tool. Tune needs a bit of work through the mid range where it gets a bit lean through the transition, but full throttle is about 12.5:1 so not far off, but it should be only a few tweaks away. Carbs are dead simple to tune so there are no problems getting it right, plus I put in a wide band sensor and guage to make my life easier. I'll do a bit of a write up when I'm happy to show how it's set up and the tune I put in it.
#33
_oldjohnno_
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Posted 29 August 2014 - 08:01 AM
Over the last ten years or so I have fitted flatslide carbies to several offroad motorbikes and without exception every conversion has been a big improvement. Each time the standard round slides [mikuni, dellorto and amal] were replaced with a flatside and no other changes. I have used Keihin , Mikuni and Dellorto flatslides and although they are very similar I would say the Keihin was the best. The mikuni and dellorto look to be better quality but the Keihin just seems to work that little bit better.The Dellorto was the hardest to jet, which is unusual as their round slides are possibly the easiest and most consistent. Keihin and Mikuni jets and parts can be purchased from Show and Go[in SA in think]one day turnaround on orders. Overall performance increase [seat of pants feeling] would be in the order of 15%. The off idle response is cleaner and crisper, the mid range hit is bigger and they rev harder, in other words better everywhere. They also are a little easier to jet, the only downside is they use a fair bit more fuel, as these are competition bikes that is not a problem.
Cheers Greg
My experience has been the same Greg, and the PWK Keihin - especially the Air Striker version - seems to be the current favourite of the dirt bike set. Still, the HSRs are particularly suitable for 202s as they have been specifically developed for four-strokes of that cylinder size. And I still have a soft spot for the good old Mikuni VMs - maybe not the fastest but easy to tune and absolutely bulletproof. I've been buying Mikunis from Niche Cycle Supply (they have an ebay store), they have very good pricing and a huge range of carbs and parts.
#34
Peter UC
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Posted 29 August 2014 - 04:34 PM
The main think I found with mine was to block off the pipes between the manifold runners, they sort of acted like a plenum and it was not happy a low RPM until they were blocked off, I'm just using a Redline SU manifold. When I sent the car off to get tuned, apparently it was difficult to get them balanced right. But aside from that they have been good, economy has not been too bad considering the size of cam I have in it. Throttle response is really good and they are pretty easy to tune. The cam is an approx. 240@050 solid cam and it idles fine at 800-900RPM and doesn't complain above 1700-1800RPM.
Let me know if you have any questions
#35
_Sir LC_
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Posted 30 August 2014 - 09:22 PM
Cheers for the advice on the manifold.
When you say doesn't complain above 1700rpm, are you saying that its a bit flat/sluggish? from 900-1700rpm?
Do you recall what jetting you ended up with for your combo?
Any pics of the final setup, linkages etc.?
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