suzuki gp100 tuning

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suzuki gp100 tuning

i just bought a suzuki gp 100 and am interested in tuning it and cannot seem to find any info any ideas ???

They're more of a commuter bike than anything, GP by name but not by nature but should still get over 70mph in good order which is more than enough for the running gear. Just bring it up to standard scratch- a good thorough service, treat it to new rings and/or piston and give the exhaust a decoke and it should run a lot better. Invest in a manual and you won't go wrong they're easy enough to work on.

shove the 125 engine in it

buy some old PB (?) mags. I think they did a GP100 project years and years ago :burnout:

my mate had a gp about 20 years ago when we were all Learners. he did loads of tuning to the engine but he was shit hot. did all the porting work himself. standard 125cc (not bored) opened the disc valve as far as it could go, stuck a rg 500 flatslide carb on with a piece of stocking for a filter. think it had an X7 front end & back wheel. good for 100mph (complete with L plate)and the acceleration was rapid. bottom end used to complain a lot though. always having to rebuild it................ahhhhh it was great being a learner in the olden days

motopat wrote

buy some old PB (?) mags. I think they did a GP100 project years and years ago :burnout:

That was the 125, tuned by John Robinson.Might struggle getting a 1985 back issue of PB though

motopat wrote

buy some old PB (?) mags. I think they did a GP100 project years and years ago :burnout:

demographic wrote

That was the 125, tuned by John Robinson.Might struggle getting a 1985 back issue of PB though

Only question remaining is whose pipen slippers I had best fetch first??Aaron - born december 1983.

blessmycg wrote

Only question remaining is whose pipen slippers I had best fetch first??Aaron - born december 1983.

I only knew cos there was a picture of it in this octobers issue

blessmycg wrote

Only question remaining is whose pipen slippers I had best fetch first??Aaron - born december 1983.

you young whippersnappers..........nuthin' but cheek.:smoke: if i could get out of this chair i'd.............................

Tuning a GP100 - I did this to a 1978 proper disc braked one.Barrel - it can be overbored to 56mm, mine was 51mm.Also raise the top of the exhaust by 1 or 2mm, widen by a similar amount and smooth it, smooth all the transfer ports as well, flowing these alone will give around 1/2bhp.Fit a 102.5 main jet and a B9whatever spark plug. 16 tooth front sprocket.The rejetting, plugs and gearing are essential for the Micron expansion pipe.End result is a GP100 capable of a genuine 80mph and at least 15bhp. Moderately reliable, but then I had enough money to get a 250!!If I had kept it I would have fitted a 125 piston! and bored the carb out.Timing must be spot on or pistons will melt.

Performance was. Beat a CB125T, a GP125 with some tuning, and got over an indicated 90. The genuine 80 was achieved and then I ran out of road still accelerating.Used to just keep up with friends 250s and was one of the quickest 100s at the time.

mji wrote

The genuine 80 was achieved and then I ran out of road still accelerating.

Short road then?

I had a tuned GP100 back in the mid 80's.Went through a lot of pistons and bottom end rebuilds.You'd be better off spending your time and money passing a test and buying a bigger bike IMHO.

I've just joined.This is the PB GP100 you've been on about.

Dymags on a GP 100?Thats top quality, tell us more

Good find that man. welcome to VD. now get over to general and get broke in.I'll have a black coffee thanks.

Wow, that brings back some memories. I can remember the feature in PB, great to see it's still about and looking fantastic

Hi, new here. Does anyone know where i could find a performance exhaust for my gp100, seems near impossible to find?

demographic wrote

Dymags on a GP 100?Thats top quality, tell us more

Here's a photo from Oct 86 PB when it was originally finished.

davej106 wrote

Here's a photo from Oct 86 PB when it was originally finished.

Good stuff

fastfitter wrote (see)

mji wrote

The genuine 80 was achieved and then I ran out of road still accelerating.

Short road then?

Tamar Bridge

gp100rob wrote (see)

Hi, new here. Does anyone know where i could find a performance exhaust for my gp100, seems near impossible to find?

Contact Micron and ask - they were good but noisy

HiI need to set the timing on the GP100 (points model).   I've got a strobe to check it.  However, the magneto has 4 timing marks on it - all close together, and marked A, B, C and M.  Anyone know which of these I need to set the timing to? Cheers Lee

i have just aquired a free gp100, its been messed about with and i have just got it started.issue is its chucking out loads of oil into the exhaust and smoking loads.any idea why?i am using smokeless 2 stroke oilputoline gear oilnew sparkpiston head and cylinder are fine.oil pump is set to factory settings (according to haynes manual)i have been told that the crank seals are gone and its leaking gear oil into the head, can this be true?

It's not leaking oil into the head as such: On the induction stroke (piston rising, intake ports uncovered) it's sucking fresh air fuel mix into the crankcase, but is also sucking in gearbox oil thru' the crank seals.At the end of the power stroke the transfer ports are uncovered and it's this oil-rich mixture that goes up to be burnt in the combustion chamber.So you could argue it's actually pumping gearbox oil into the head .

 My first bike was a GP 100, bought brand new in August '79. I must admit to abusing it terribly, but I loved that bike. Never got into the cleaning stuff, but I rode it all the time and still have great memories of it. Talking tuning, a mate of mine had some rotary files and raised the exhaust port, though it was pure guesswork. Other than that, I just had the tiniest pair of drops that were so tight the choke lever hit the tank. As for stuff like micrins and rear sets, I never had any. My money went on petrol, fags and Marston's Pedigree. Until it finally blew up about 18 months after buying it (main bearings and holed piston combo) I must have fallen off it at least once a month trying to keep up with my mates on 200s and 250s. However, the blow up was fairly terminal at the time because my party lifestyle meant I'd been sacked and couldn't afford to repair the bike. When I did get a job again I bought an X7, so the GP never did get fixed. Fact is, I've still got most of the GP now. A box full of bits in the back bedroom, the frame and one wheel (no idea what happened to the other) in the garage. I really should get round to bringing the little beauty back to life.

A digital chadbapsle-caliper would be ideal for this. 

 A what? BTW if anybody's got any GP bits I could well be interested.  I'm getting the bug again.

Hi I have a gp 125 complete less the head barrel piston carb.Thanks Neil

Always found the Allspeed a better option than the Micron. I still have my GP100, 125 barrell, rotary disk cut, ported, ledar kit, ram air and a big jet and extra tooth on front sprocket.  OK for an indicated 90 "prone" as they used to say.It's an old V reg and I have had it 21 yrs now. Feel free to ask if you need any help.

hey chaps, im looking for a carb jet needle for the GP125 marked 4EJ14 any one got any lurking? im going a complete rebuild of the GP100 with a GP125 head n piston. Post some pix if any one asks..thanks in advance. and this is my first post.. HI!

Neilypvs,

Which town are you in mate? I'm near Derby. I could be interested in your GP.

i have two gp100, one red, one yellow...one was running before i started to strip it, it has spoke wheelsthe other was a non runner, just wanted it for the alloy wheels, seat, plastics, light cluster, forks and some other bits, both bikes have complete engine.one had full electrics the other has no lighting.two exchausts, new bars, new rear shocks, two carbs in great condition, choke spring in one needs renewinglots of new cables and bolts, will need van to collect as both bikes are in parts, i have the haynes manual also.great project started but baby forces sale.have spent about £150 on all parts so far so make me an offer.bike is in hendon, which is north london.like i said, one working bike the other spares.

I have just bought a GP 100. 19,000 kms from new. I have not a manual yet and wondered what capacity and type of gearbox oil it takes? I'm onpickteam@xnet.co.nz   if anyone can help. Thanks.

Does anyone know the standard jet sizes for the GP 100 carb please? I'm on pickteam@xnet.co.nz  Thanks.

Hope someone can help me with my GP100. It is a 1984 model and seems to have a CDI fitted since I cannot seen any points and it has a very CDI looking black box under the left hand sidepanel. Does this sound correct/possible? It is very sluggish below 3500 then takes off like a thief with a handbag. I've cleaned the carb/jets and tank/tank filter. Could it possibly be the air filter (looks clean), or maybe the ignition coil? I'm on pickteam@xnet.co.nz if anyone can help.

Sounds more likely to be just a typical 2-stroke power band, or possibly it's running a little rich and lower rpm and bogging down a bit? Try opening the throttle more gently / slowly and low engine speeds and see if this helps.

Kiwi Glyn...where abouts in NZ are you?  I'm in Wellington.I've got a GP100 that I'd put in a RZ50 frame and raced it in F4.  My one has a CDI but I don't suffer from a lack of power down low...the inle, transfer and exhaust ports have been ported and it's got a knife edged crank.Also, the casing around the carb has been cut away to help it breath.According to the Haynes manual, Transmission oil:Dry: 850ccAt oil change: 800ccSAE 20W/40

Hi Sligshot, I'm in Glen Eden, Auckland. Ta for that info. Do you know what the standard size main jet and needle clip position is please, on the std carb. I've got a 97.5 jet in there at the mo.  I'm on  pickteam@xnet.co.nz  if you could mail me that would be great. Cheers  Glyn.

right guys, just finishing a nut and bolt rebuild of my gp 100, had the frame blasted and resprayed in 2 pack, polished casings, micron pipe, new chrome everywhere, in short a minter, having the seat base blasted and powder coated this week and having the tank blasted ready for re-spray at same time, would like to respray in the original blue and re-fit the x model decals, but where do you get them from, tried everywhere, also is the main jet supposed to be a 102.5 as listed above for the micron?, looking for a 125 barrel if anyone has one!!please, might respray in red yet though, any ideas what looks best?? aany advice always appreciated, jalsport@hotmail.co.uk

Try sunrisegraphics, they should be able to help. Is it your pipe on the bay for sale?

yes thats the one and its my bike on there, keeping it standard now, what ya reckon

Right guys, got the gp running lovely now and have decided to keep the micron as they are rare as hens knackers, the bike trult is a minter now its restored and i,l never sell it so the microns a must for that little bit extra oomph

I have just brought an "83" GP100 that has a few problems hope somebody might have some good advice...Issue one it has a Micron exhaust fitted and is running the standard 105 main jet,But whoever fitted it has moved the needle to the top notch.Somehow i don't believe the jet size nor the needle adjustment are correct Anybody know what jet and carb setup this should be running?Secondly when riding the bike at about 6,500rpm for 20 seconds or so it seems to die....But if you drop to around 5,000rpm it rides as normal..It also seems to have oil coming out of the exhaust when riding, i presume this is gear oil for some reason..How do i cure that problem..I remember these in there heyday and they were quite a quick bike with tuning....Hope i can get this one running sweet..Any help would be well appreciated...Email address is /forum/smilies/confused_smiley.gif[/img]tuartholmes20@btinternet.com]stuartholmes20@btinternet.com

hi there, 105 main jet standard ????? should be 97.5 standard on the gp100, mines fitted with a 102.5 main jet now which is advised for the micron, sounds like yours is running too rich and your float height is too low for the fuel to keep up with the rich demand, try a 102.5 main jet from wemoto, also check the air filter is clean and not clogged, if its your oil coming in from the gearbox then its total strip down and separate cases and fit new crank seals, couple that up with the needle on top notch and its any wonder its not right, try all of these ive suggested and let me know what happens, p.s also make sure the points gap is right, cheers jon

Thanks Jon..So i should fit a 102.5 main jet and then adjust the needle to the second notch..As it should have been originally,and the air screw at 1 and a half turns out..Is that right...I suppose then if i am going to the extent of stripping the engine to do the crank seals its really at the point of a complete engine rebuild then...As for the air filter when i got the bike and had a look at the air filter i found that to be and old sock wrapped around the metal cage.I have obviously replaced that with new sponge..Looks like either way it will be a long and exspensive job really..Question is do i bother to rebuild it or not......Cheers Stuart

Stuart, if your bike is half tidy then i,d go the hole hog and so it rightm then you know its done, parts are,nt that expensive, but try the jet first and check your oil pump is lined up properly as it could just be over oiling which funnily enough will cause the same symptons as your describing to me, its easy enouh , just line the pump marks up and ste your throttle to half way and your done, as for the needle i would drop it to the bottom notch first and go for a ride and when your 200 yds from home kill the throttle and caost home take out plug and check for condition, too black = too rich and so on , then adjust needle from there, good luck..

Thanks Jon...Been tinkering about with the bike all day again....Today have added a 102 main jet and put the needle on the second notch from top..Checked the oil pump marks which when the hole is at the top on the carb slide the oil pump marks line up on the pump so presume its right but still getting some oil out of the exhaust obviously 2 stroke oil un burn't...But still dies at 6,000rpm after 15-20 seconds or so....But the other problem i have now encountered aswell is the electrics packing up on the lights/horn and indicators as when the indicators are switched and the bikes in neutral the neutral light and indicator warning lights flash....Also the battery goes flat so must be some electrical fault somewhere aswell,Getting fed up with the thing at the moment..As for the bike its the one that is still listed on ebay at £700 red with top box and micron...Thanks for the continuing help.........

wow £700, thats hoping a bit ,not being rude or owt, but i,d be happy with that for mine and thats newly restored and absolutely as new, have you an original exhaust to put on and try ? i think your bike dying at 600 corresponds with your electrical problems , i think your losing spark etc at those revs, try a new regulator aswell and a rectifier, if all else fails i,ll buy the micron from you, i have a brand new nos gp 100/125 exhaust here i,ll trade for it, cheera again, jon

No i didin't pay £700 for it but i paid £600.....The problem is when you buy a bike from somebody you can't pull it to pieces on there drive (unfortunately) so all the bodges over the years are all hidden under the panels/Seat/tank etc...The thing is electrics aren't my strong point at all.....At the moment it runs fine on tick over and at 3-4,000 rpm on the stand but its obviously an electrical fault so sounds like a trip to the local bike shop to see if they can sort it...(could be exspensive knowing my luck)no i seem to remember the old saying (JAP CRAP!)  and have ago heros bodging stuff up over the years.....Don't i wish i could go back 2weeks i'd have given the bloke £20 to keep the bike... weird thing is he's about 40 years of age and works as a salesman at a motorbike shop....

Look !! buy a haynes manual and go through things step by step, check and double check everything, they are good bikes and are fast becoming somrthing to hang on to in good nick like mine, look at gt125 and gt 185 now, a minter will see them selling for a grand easy, i got a gt185 as my next re-build to do this winter, 4500 miles from new, dont give in .. cheers jon

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