Manky Monkey Motors

 I have been toying with the idea of fitting a set of cbr600 jelymould carbs on a 850 reliant, i want this engine for a trials car and lively response and smooth flexibility is my main goal in any development.
   Now i have a few additional ideas to try along with the carbs but want to get the carb issues out of the way first so as not to get bogged down.
     Is it worth the effort fitting bike carbs, fitted some to a crossflow 1300 and it felt very torquey over any other carb install i have encountered on those engines.  The Reliant being a sort of Alloy A Series bread and butter sort of engine i am not expecting earth shattering improvements just trying to make the best of what is there.  I asked similar questions on the R3W forum and got some worthwhile input and it was pointed out to me some on this site had Reliant carb mods implemented successfuly. So your thoughts and observations on the proposed carb fitment, and of corse any hints advice on the actual install would be great.

BigDogSix & Steve Brock might be the people to talk to.
Faster acceleration seems to be the main improvement, though I've no idea how it affects fuel consumption/top end speeds etc.

look at steve brocks build hes done the cbr 600 carbs on his reliant trike project,
also thebigdog6 has now a bike carb set up on his reliant trike.."a tale of two trikes"
im not sure of any power gains but on the trikes they look smart and different ...for now ;)

aaahhhhhyyyyyy type a bit slower :D :D

Just confirming your thoughts mate.  ;)

If its a 'trials' type of motor your building then response and flexibility, not out and out top end, should be the aim, as with trials bikes, so one 1.5" or two 1.25" S.U's would be more suitable, unless its just about "cosmetics!" again................Morrag

I have found that with the bike carbs the trike picks up a lot faster but i would not say the top end has changed much at all just gets there faster but that could have been because of the extensions i had on my SU but im no expert . I have since fitted some air filters and this has altered the performance again and i have had to remove the ram pipe thingies as there was a massive flat spot at the top end which i suspect is because the were too close to the top plate of the filter . I have to admit i am generally very happy with the bike carbs and the do look the dogs  ;D

 Thanks a lot for the honest replies, i can see where you are coming from big dog six and what you say is borne out in what i have seen in the ford crossflow install.
    I do also see where morrag is coming from with the SU carbs, I did consider replacing the std su with one of a pair off an MGB engine i have laid about,  and doing the web chop job betweeb 1 and 2 and 3 and 4 ports,. this from all i have read on the net actually works on these little engines.
   Any detail and measurements on the cbr 600 to Reliant  manifold fabrication or is it just trial and error.
    One other mod i had planned was to retard the camshaft a few degrees to help improve torque at the expense of a little top end. This does work again on the small fords and i guessed may work on the Reliant. All the fun of the fair aye and some.  ;D

 Have any on this forum actually done this reliant manifold mod??http://www.athz90.dsl.pipex.com/voyager/Manifold/manifold.htm.  I have a spare std manifold  but input from some one who s done it would be good.

link doesnt work, but this is the very same ad i came across a few week ago they recon the results speek for them selfs, there was 1 on ebay a month ago fetched good money, i thought about it with mine but havnt yet done it, i could do with buying a spare as youve done, but yeah go for it and lets here first hand results. i read on a rolling road they really saw the gains

 Well ok i will butcher it then, i have a complete spare motor so should be ok for sacrifice  just the manifold.
   It makes good reading, but sort of goes against the grain sort of interrupting the flow like that, heck the Reliant s manifold must be really really poor that is all i can imagine, in which case i suppose anything will improve matters to some extent.

http://www.athz90.dsl.pipex.com/voyager/Manifold/manifold.htm


Thats a common mod is that.

is there a certain size the slit/hole should be??  and depth??

That mod works  :)
I do  mine to a depth of about 1/2 inch but probably anything up to an inch depth would be fine .
However , I taper the bottom of the cut and radius all the sharp edges .
You also have to modify the cylinder head inlet to remove the sharp edge between the ports and modifying the inlet / exhaust manifold gasket .
More power can be gained , if keeping the original exhaust manifold , by opening  out the bore and smoothing the tracts as per
http://www.mankymonkeymotors.co.uk/forum/index.php?topic=10694.0
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PS ; Another school of thought is as per the following link ;
https://sites.google.com/site/fifersrelianthintsandtips/kitten-related/inlet-manifold-modification
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i did the exhaust as your link just because when i put a new gasket on it was miles away from matching it took but 10 mins with the die grinder. i will now be doing the cut away manifold, not brave enough to do much more untill i get a spare as you know with the luck i have on my build somthing will go wrong. 

 Well i hacked the inlet manifold about as the photos show, i even ground out the carb adapter and flange as close as i could guess from the pictures. Set the carb up with the lift pin, it runs well, i do genuinely think it as more grunt dare i say torque,  but the most noticeable thing is the engine sounds different. i have changed nothing other than the manifold mods and was surprised by this. It seems to pulse / burble in the exhaust kind of deeper. ???
    Anyway i don't know why it does but it does, now is it a success? . A definite Yes. I do believe what they say about this mod is valid, If i could turn back the clock would i still do it, yes i would i had spare time and used it enjoyed doing it, and i think it is better.

And what is more i am going to carve out a old std 1300 ford crossflow manifold exactly the same style just to see if it as the same improvements there on the ford lump.

Glad you have found an improvement  :)
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where is this lift pin ive been searching and never found it... did some hs2 carbs have it and some didnt??

see last post on this page

http://www.mankymonkeymotors.co.uk/forum/index.php?topic=10883.msg138266#msg138266

 I think they all have a lift pin but could be wrong. The lift pin is located on the underside of the main carb body just to the right of the float bowl, and just forward of the left hand air intake bolt. its a small spring loaded pin, to set the carb get the engine idling at a normal tick over warm etc. then quickly lift the pin up if the engine revs drop and the engine stalls it is too lean if it rises and keeps on rising it is too rich. it should rise momentarily and return to a smooth strong idle quickly, then it is near enough.

Yes ,as per pic below .

(http://i423.photobucket.com/albums/pp316/fifer3w/CARB%20DETAILS/CARBWITHOUTTHELIFTINGPINSHOWINGUNDRILLEDBOSS-1.jpg)
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yeah mines undrilled then like the picture, will lifting the piston with a screwdriver a tad do the same trick??

Could be a bit unreliable on the stroke /amount of lift. I dont think it is an exact science the lift pin set up but it as always worked for me on the sus. Single sus that is, the twins are another ball park, a hose and listen then, i always found it hard  on the MGBs setting up the twins. As with all things experience wins the day. 

as you say some people found setting up the twin su,s a problem  but i got pretty good at it even on range rovers
must admit i havnt set a pair up fo a couple or three years,,